No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The economic value of South African kelp forests and temperate reefs: Past, present and future
Abstract
In South Africa, kelp forests and associated temperate reefs dominate the nearshore subtidal zone in the southern Benguela, with kelp forests covering approximately 1000 km of the coastline. These ecosystems provide a range of goods and services that are of immense ecological, social and economic importance. A number of valuable species on these subtidal reefs are overexploited and have reached a state of crisis since the 1990s. Many linefish stocks are considered collapsed or overexploited, West Coast rock lobster populations are estimated to be at < 3% of pre-exploitable biomass and abalone are similarly overexploited, with two of the four major historical fishing grounds now closed to fishing. The current value of this ecosystem is estimated at US 290 million year− 1 (ZAR 3.9 billion year− 1) contributes to the South African gross domestic product (GDP), with ecotourism contributing almost 40% of this, followed by recreational fishing (28%), and commercial and illegal fishing (c. 15–16% each). Income currently generated by fisheries is greatly reduced, with some sectors worth less than half of their value in the 1990s. Indirect ecosystem services are valued at US$ 144 million year− 1 (ZAR 1.9 billion year− 1) but aren't realised in the country's GDP as they do not provide direct economic value. Given the importance of the Benguela nearshore region to low-income coastal communities, particularly in the face of increased climate variability, striking a balance between rebuilding depleted stocks and meeting the socio-economic needs of those reliant on them will require a renewed focus on coastal research, with an emphasis on co-ordinated interdisciplinary projects.
... Kelp (large brown macroalgae mostly of the order Laminariales) is a source of food and refuge for several organisms, and a nursery for invertebrate and fish species (Steneck & Johnson, 2014;Teagle et al., 2017). It forms extensive forests that provide goods and services to humans, such as food and tourism (Blamey & Bolton, 2018). Kelp is becoming a marine tourism resource for diving experiences (both scuba and/or free diving and snorkelling) and kayaking in Cape Town (Scuba Diver Life, 2018). ...
... These circumstances make it relevant to establish baselines that can be monitored over time and compared with kelp trajectories in other regions. Additionally, South African kelp forests have been subjected to stressors such as wastewater pollution, the expansion of alien species, grazing by sea urchins, and overfishing of commercially important species associated with kelp (Blamey & Bolton, 2018;Lindberg et al., 2020;Morris & Blamey, 2018). Long-term monitoring would contribute to understanding kelp responses to these stressors and the management of local kelp forests. ...
... This organisation offers snorkelling CS days or scuba diving in kelp forests for shark identification involving participating interns. Given the abundance of kelp forests around Cape Town, and the presence of several organisations and companies offering marine and coastal tourism in the area (Blamey & Bolton, 2018;Pfaff et al., 2019), there is potential to increase the pool of kelp CS tourism activities. Additionally, given the halt of international tourism resulting from the COVID-19 pandemic, tourism research has been called to pay greater focus to the development of national tourism markets and forms of tourism such as 'slow tourism' (D'Agnessa & Lucrezi, 2022). ...
... Kelp forests dominate 2500 km of the southern African coastline, forming a highly productive coastal ecosystem referred to by some authors as the 'African Seaforest' (Blamey and Bolton 2018;Dunga 2019). The African Seaforest differs from its global counterparts due to complex environmental gradients resulting from the dynamic interactions of the warm Agulhas and cold Benguela currents (Field and Griffiths 1991;Wepener and Degger 2019). ...
... This material was initially exported for alginate extraction, a practice that declined from ∼2500 dry t in 1986 to ∼290 dry t per year today (Department of Forestry, Fisheries and the Environment [DFFE] data, mean for 2017-2021). Blamey and Bolton (2018) estimated this sector of the seaweed-based economy to be valued at US$0.03 million per year. Later, soil treatment and animal feed applications also developed (Anderson et al. 1989). ...
... The first major development that resulted in a thriving seaweed economy in South Africa began with the company Kelp Products Ltd. and their development of Kelpak, which today comprises a range of biostimulants and liquid fertilisers. The consumption of harvested E. maxima for this application is ∼2000 fresh t per year (DFFE data, mean for 2017-2021) and is worth US$0.29 million per year (Blamey and Bolton 2018). The mass of kelp harvested for biostimulants and fertilisers will soon overtake the amount harvested for abalone feed . ...
Kelp forests dominate the western and southwestern coastlines of southern Africa. This expansive ecosystem spreads over two very different ecoregions that are of particular interest to researchers due to the complexities of their physical environment. The mid-to-late 1900s saw a proliferation in pioneering research on southern African kelp forests. Since this period (1970-1989), researchers have published comparatively few seminal studies concerning kelp forest ecology and biological functioning. In light of this deficit, this review synthesised pre-existing research on southern African kelp forests, and highlighted key gaps in the research landscape to spark interest and facilitate new studies. Among several others, key research gaps uncovered by this review include kelp carbon sequestration potential and possible contributions to the blue bioeconomy; deeper exploration into the biological functioning and ecological roles of Macrocysis pyrifera and Ecklonia radiata populations in southern Africa; and the impacts of a changing physical environment on these kelp forests. In light of our rapidly changing climate, filling these gaps will be essential in informing conversations around coastal and marine management decisions and policy.
... Kelp forests are assemblages of large brown algae, predominantly of the order Laminariales (Blamey & Bolton 2018, Smale 2020. They are found along 25 % of coastlines globally (Wernberg et al. 2019), covering an area of 49 287 km 2 (Eger et al. 2023), dominating rocky reefs in shallow temperate oceans and thriving in cold, nutrient-rich waters (Teagle et al. 2017, Wernberg et al. 2019, Jayathilake & Costello 2020. ...
... They also influence water flow, light levels and sedimentation (Smale et al. 2013), and support complex trophic webs due to their high levels of primary productivity (Dayton 1985). Ecosystem services provided include fisheries production, carbon storage, coastal protection and nutrient recycling (Blamey & Bolton 2018, Schoenrock et al. 2021, Eger et al. 2023). These services, alongside education and recreation services, are associated with high economic value, including for fisheries, tourism and climate regulation (Tegner & Dayton 2000, Bertocci et al. 2015, Bennett et al. 2016, Bayley et al. 2021. ...
... These services, alongside education and recreation services, are associated with high economic value, including for fisheries, tourism and climate regulation (Tegner & Dayton 2000, Bertocci et al. 2015, Bennett et al. 2016, Bayley et al. 2021. The value of kelp forests and associated rocky reefs in South Africa has been estimated at ZAR 5.8 billion (USD 434 million) per year, emphasizing their importance to the national economy (Blamey & Bolton 2018). To properly manage kelp as an economic resource and to preserve the ecosystem function of this biogenic habitat, it is essential to fully understand the diversity and ecological interactions associated with kelp forests. ...
Kelp forests along the southwestern and west coasts of South Africa, dominated by the species Ecklonia maxima and Laminaria pallida , are locally termed ‘the Great African Seaforest’. They form 3-dimensional biogenic habitats that provide 4 distinct microhabitats—canopy, fronds, stipe and holdfast—with the latter typically supporting the highest abundance and diversity of associated macroinvertebrates. The macrofauna inhabiting kelp holdfasts in South Africa have rarely been studied, resulting in a near complete lack of baseline data. In this study, macrobenthic assemblages from 40 E. maxima holdfasts were examined over 2 marine ecoregions and 4 locations. Macroinvertebrates were identified and counted for univariate and multivariate analyses using family-level data. A total of 120 families from 9 phyla were identified and were generally dominated by Arthropoda (48 families), Annelida (24 families) and Mollusca (23 families). Marine ecoregion had no significant effect on composition of macroinvertebrate assemblages, whereas location had a significant effect. There was no significant relationship between holdfast volume and macroinvertebrate diversity or abundance, suggesting that other environmental and physicochemical factors are important in determining community structure. This study serves as a baseline for future research aimed at understudied holdfast macroinvertebrate communities in the Great African Seaforest.
... Among other functions, kelps enhance local biodiversity by being foundation species that create biogenic habitats and facilitate complex biological interactions (Dayton, 1985;Steneck andJohnson, 2014, Krumhansl et al., 2016). Their role as habitat providers include many commercial species with high economic value (Blamey and Bolton, 2018;Vergeś and Campbell, 2020). In particular, abalones and lobsters are typically regarded as the most important commercial fisheries linked to kelp forests, generating millions every year worldwide (Smale et al., 2013, Bennett et al., 2016, Carr and Reed, 2016Blamey and Bolton, 2018). ...
... Their role as habitat providers include many commercial species with high economic value (Blamey and Bolton, 2018;Vergeś and Campbell, 2020). In particular, abalones and lobsters are typically regarded as the most important commercial fisheries linked to kelp forests, generating millions every year worldwide (Smale et al., 2013, Bennett et al., 2016, Carr and Reed, 2016Blamey and Bolton, 2018). The best estimates of the value of the ecosystem services (e.g., fisheries) provided by kelp forests are from South Africa and Australia. ...
... The best estimates of the value of the ecosystem services (e.g., fisheries) provided by kelp forests are from South Africa and Australia. In South Africa (Blamey and Bolton, 2018) and the Australian Great Southern Reef (Bennett et al., 2016), it has been estimated that kelp forests generate a revenue of 434 million/year US$ (427 million/year €) and 1,066.4 million/year AU$ (726 million/year €), respectively, of commercial/recreational fisheries. ...
Kelp forests are critical habitats for temperate coasts that are experiencing dramatic declines worldwide in recent decades. Yet, even though they often support wildlife populations of high socioeconomic value, the consequences of kelp forest decline for small-scale fisheries (SSFs) have received surprisingly little attention. Here, we take the first step to fill this gap through the local ecological knowledge (LEK) of SSF fishers whose fisheries are associated with this habitat in NW Spain. LEK was used to 1) estimate kelp forest loss, 2) identify the main fisheries associated with kelp forests, 3) gain insight into the changes these fisheries may have undergone in recent times, 4) evaluate the economic importance of kelp in the study area, and 5) describe the commercial chain of exploited kelps and relevant fisheries related to them. Fisher’s knowledge of kelp forests was documented through interviews with the help of a semi-structured questionnaire with open–closed questions about the small-scale fishery and its target species. Additionally, participants were asked to map the current and former (20 years ago) distribution of kelp forests in their fishing area. Results show that a range of fish, crustaceans, mollusks, echinoderms, and even the kelp itself are fished/harvested in the study area, suggesting the socioeconomic value of those species. The most intensively targeted species usually belong to fisheries with high commercial value, and first-sale data indicate that they are worth some 10 million euros to the local economy. On the other hand, compared to two decades ago, fishers reported a substantial contraction in the area occupied by kelp forests and decreases in the fisheries typically associated with this habitat. Landing data partly support this perception of a decline in catches. Altogether, this information will be useful to foster kelp forest conservation and to evaluate their socioecological and economic implications for SSFs.
... This would call for research on kelp diving tourism, starting from segmentation. Studies have synthesised the economic value of kelp forests, including kelp tourism [13], [14]. The economic data from these studies suggest that kelp diving may be significant, and thus relevant to understand and monitor to ensure its management and sustainable development. ...
... This documentary could draw attention to South Africa for kelp tourism including diving, which may represent an important factor of coastal and marine tourism in the area. Some research suggests this, although only indirectly [13], [15]. Thus, segmentation research on kelp diving is timely, given a research gap concerning this niche activity as well as cold-water recreational diving in general [9]. ...
... The origin of the participants suggests that kelp divers in South Africa (it must be considered that this study happened during the closure of the country to international tourism) are local and from the Cape. Kelp forests can only be found in the cold-water regions of South Africa and around the Cape Peninsula [13], implying that the divers dived their local coast. This result also suggests attachment to the local coast, encountered in other cold water diving research [22]. ...
Recreational diving is an important part of marine tourism and has been extensively studied, especially in the context of warm-water and tropical environments. Comparatively, research on diving and the segmentation of divers in cold water habitats remains scant. Ever since the award-winning documentary My Octopus Teacher came out in 2020, more attention has been drawn to kelp forests, which are typically cold-water habitats. Diving in kelp is a recreational activity that has the potential to become a major part of marine tourism in countries like South Africa. However, limited research exists on this
niche type of diving. This study aims to segment and profile kelp divers, to guide the sustainable development and management of kelp diving as marine tourism activity. To reach this aim, qualitative research was conducted. Specifically, semi-structured interviews were used to gather data on the demographic, psychographic, behavioural and specialisation profiles of 50 divers in Cape Town. The divers were male and female in similar proportion, they were in their late thirties and had tertiary education. They were mainly from South Africa and resided in Cape Town. They were both scuba and free divers and moderately specialised. Motivations to dive in kelp included observation, being in nature, relaxation and escape, adventure and exercise, discovery and learning, and photography. Experiences diving in kelp were relaxation and wellbeing, awe and wonder, contact with nature, freedom, novelty, feeling safe, and social interaction. The divers ascribed extrinsic and intrinsic values to kelp and recognised ecosystem services of kelp forests. They were also aware of problems affecting kelp and could propose viable solutions to combat these problems. The divers showed strong conservation commitment and place attachment to the local coast and kelp forests. The results were
used to make recommendations concerning marketing and management, including better patrol of kelp forests, codes of conduct for divers, education, and marketing of sustainable kelp diving and other nondiving activities.
... Kelp forests provide a wide range of essential ES (Wernberg et al. 2019): ES of direct-use benefits for human well-being (e.g. kelp harvesting for alginate extraction, providing habitats for commercial and recreational fish species, tourism; these are ES that contribute most to the high economic value of kelp (Blamey and Bolton 2018)) and of indirect-use benefits from the underpinning ecological processes (e.g. climate regulation, carbon sequestration, coastline protection, nutrient cycling; Krause-Jensen et al. 2018) or from their non-use value (e.g. ...
... We then used the conversion from FW to DW (Equation (2.2)) to estimate the total quantity of N and P absorbed by kelp: (Laffoley and Grimsditch 2009). They do not contribute to long-term carbon storage or mitigate against climate change, however, because they cannot store carbon below ground, and their turnover is extremely rapid, with most of their productivity being remineralised (Blamey and Bolton 2018), consumed, or decomposed (Krumhansl and Scheibling 2012). Nonetheless, kelp may play an indirect but significant role in carbon sequestration through photosynthesis by acting as carbon donors to recipient "blue carbon" habitats (e.g. ...
... We classified "water oxygenation" as an indicator of "regulation of the chemical condition of salt water by living processes" ES (Filbee-Dexter and Wernberg 2018), which encompasses all the associated impacts, and whose indicator corresponds to the quantity of O2 (in tons) released by the kelp. As O 2 (in tons) is released through photosynthesis at the same time that carbon is fixed, we considered the rate of associated O 2 = carbon fixed � 36 12 (Vassallo et al. 2013) and multiplied it by the quantity of carbon fixed by kelp: (Løvås and Tørum 2001;Blamey and Bolton 2018) and are assumed to protect the coastal shoreline from erosion and storms by changing the flow, sediment, and energy that pass through the system. However, the degree of ecosystem protection is non-linear (increasing as plant density increases), multifactorial and context-dependent (Pinsky et al. 2013). ...
Kelp forests, primarily Laminaria digitata, provide a broad range of ecosystem services of high social, economic, and ecological value and are considered one of the most productive ecosystems on the planet. Several studies have shown that kelp ecosystems are regressing in response to multiple stressors, especially climate change, which could lead to local extinctions. This may induce a decrease in the ecosystem services provided. Many studies use ecological niche models (ENM) to project potential future species distributions under climate change scenarios; however, no study has projected the future supply of ecosystem services resulting from shifts in species ranges and changes in biomass. In this study, using French coasts as a case study, we developed a new and reproducible methodological framework that combines ENM and ecosystem services indicators to assess impacts of climate change on ecosystem services supplied by kelp. To this end, we first identified ecosystem services currently provided by kelp and then used ENM to project future kelp distribution from 2041 to 2050 under climate scenarios RCP2.6 and RCP8.5. Finally, by estimating the biomass of kelp, we assessed the current and future ecosystem services provided by kelp.
... Kelp refers to large brown algae of the order Laminariales in the Phaeophyceae class (Bolton, 2016) and is found in shallow coastal rocky habitats of temperate and Arctic regions globally, forming dense patches or forests (Bolton, 2010). Kelp forests are marine ecosystems offering a variety of services that are valued at billions of US dollars annually (Bennett et al., 2016;Blamey & Bolton, 2018;Teagle et al., 2017;Wernberg et al., 2019), such as primary and secondary production, coastal protection, and tourism and recreation including fishing and diving. What makes kelp forests attractive for recreation is their three-dimensional structure, rich biodiversity (e.g., they are a nursery ground and support communities of algae, invertebrates, fish, and mammals), aesthetic qualities, and species of fish including sharks. ...
... The case study location for this research was Cape Town in South Africa. Kelp in South Africa is mainly distributed along the west and south coast (Blamey & Bolton, 2018;Fleischman et al., 2020), including the species Eklonia maxima, E. radiata, Laminaria pallida, and Macrocystis pyrifera (Rothman et al., 2017). These species can be found along (Fleischman et al., 2020;Pfaff et al., 2019;Teagle et al., 2017;Wernberg et al., 2019). ...
... These species can be found along (Fleischman et al., 2020;Pfaff et al., 2019;Teagle et al., 2017;Wernberg et al., 2019). Kelp harvesting here is practiced under regulation and kelp forests support commercially important species (like rock lobster and abalone), many of which have been overfished and illegally fished (Blamey & Bolton, 2018). Kelp ecosystems in the area are under pressure not only due to fishing but also pollution through wastewater discharge, alien and invasive species, and coastal development (Lindberg et al., 2020). ...
Recreational activities in marine environments have many benefits, such as physical and mental well-being, contact with nature and nature connectedness. These benefits can translate into other positive outcomes, including pro-environmental behaviour and attitude and ocean stewardship. Cold-water recreation including diving (scuba and free diving) is increasingly popular, yet its phenomenology is understudied. The available research, however, shows that there is great potential for cold-water diving to contribute to those benefits that can result in a “marine mindset”. This qualitative study aimed to add to the body of knowledge regarding cold-water recreation, by investigating through a blanket assessment the motivations and experiences of independent divers in the kelp forests of Cape Town, South Africa, and their putative influence on pro-environmental attitude and behaviour. One hundred divers were interviewed telephonically in 2020 and 2021, and data were extracted and analysed using both thematic and statistical analysis. Divers were motivated by experiences including hedonism; sensorial; spirituality, reverence and gratitude; learning; connection with nature; well-being; challenge; escapism; flow; and socialisation and communitas. Specific motivations and experiences resulted in pro-environmental behaviours and attitudes. The results of this study confirmed the value of kelp diving as an activity with numerous benefits to people and marine environments and were used to delineate recommendations for marketing and management that can foster the growth of cold-water diving as a sustainable form of marine-based recreation.
... Importantly, these findings also contribute to answering the question of what happens when a system changes from kelp forest to urchin barren. While past studies focused on the functions or services related to kelp forests [15,79,86,93], the meta-analysis approach provides the counterfactual. This counterfactual is needed to perform more accurate economic evaluations [121] and guide benefit-cost decision-making [122]. ...
... We found kelp forests to have higher ecosystem functions and biodiversity than urchin barrens. The shift from kelp forests to urchin barrens may lead to a reduction in many ecosystem functions, many of which have a very high value to society [15,79,93]. Conversely, restoring urchin barrens to kelp forests will, on average, increase ecosystem services and benefit people. ...
Kelp forests and urchin barrens are two stable states in rocky reef ecosystems, each providing unique ecosystem functions like habitat for marine species and primary production. While studies frequently show that kelp forests support higher levels of some ecosystem functions than urchin barren habitats, no research has yet compared average differences. To address this gap, we first conducted a meta-analysis of studies that directly compared the ecosystem functions, services and general attributes provided by each habitat. We also compiled individual studies on ecosystem properties from both habitats and qualitatively assessed the benefits provided. The meta-analysis included 388 observations from 55 studies across 14 countries. We found that kelp forests consistently delivered higher levels of ecosystem properties such as biodiversity, species richness, abalone abundance and sea urchin roe quality. Urchin barrens supported higher urchin density and crustose coralline algae cover. The qualitative review further supported these findings, showing that kelp forests ranked higher in 11 out of 15 ecosystem properties. These findings can help guide decisions on managing rocky reef habitats and demonstrate the benefits of preserving or expanding kelp forests.
... Kelp forest systems are a dominant feature along the west and southwest coasts of South Africa. They harbor a wide array of associated species and provide numerous crucial ecosystem services (Steneck et al. 2002;Blamey and Bolton 2018), although they are also under considerable pressure from anthropogenic activities throughout their distribution (Mead et al. 2013;Majiedt et al. 2019). Due to a lack of monitoring efforts of kelp forests in recent decades, their biodiversity is likely under-described, hindering conservation and management decision-making (Blamey and Bolton 2018). ...
... They harbor a wide array of associated species and provide numerous crucial ecosystem services (Steneck et al. 2002;Blamey and Bolton 2018), although they are also under considerable pressure from anthropogenic activities throughout their distribution (Mead et al. 2013;Majiedt et al. 2019). Due to a lack of monitoring efforts of kelp forests in recent decades, their biodiversity is likely under-described, hindering conservation and management decision-making (Blamey and Bolton 2018). For instance, an initial eDNA metabarcoding study at a single sampling point in the kelp forest detected > 900 metazoan OTUs (Rossouw et al. 2024), representing nearly 8% of the total diversity recorded along the entire South African coastline (Griffiths et al. 2010). ...
Environmental DNA (eDNA) metabarcoding surveys can support the acquisition of extensive biodiversity data to support ecosystem monitoring and conservation actions. However, the optimization of eDNA metabarcoding project design is essential to capture spatio‐temporal heterogeneity of eDNA signals and maximize diversity detection. In this study, we developed a system‐specific approach to detect fish communities in kelp forests, by analyzing fine‐scale spatio‐temporal patterns in eDNA signals at two sites along the South African coastline, as well as testing the effect of biological replication and pooling of replicates on species detection. At each site, samples were collected at two stations along the shoreline at two depth zones, and this was repeated at two time points (24 h apart). We detected 113 operational taxonomic units (OTUs) across 32 families, but fewer than 20% of OTUs could be assigned to species, indicating that barcode reference libraries need to be drastically improved. We detected significant differences in communities across small spatial scales (< 600 m) and time points, suggesting that to best capture a site's diversity patterns, samples should be collected at multiple points and times within at least 24 h. To detect ~80% of the fish community, including some low abundance species, a minimum of four samples appear sufficient. In addition, a higher number of OTUs (76 vs. 65) were found in individual replicates than in any of the pools. However, pooling samples prior to sequencing can still detect valuable broad‐scale biodiversity patterns for monitoring and can offset the decrease in data resolution with the benefit of accumulating comprehensive data from increased sampling efforts over time. As a pilot investigation into how best to maximize kelp forest‐associated fish communities, this study provides a basis for optimizing sampling design for coastal eDNA‐based surveys in southern Africa and strengthens the development of long‐term eDNA monitoring programs to better support conservation and management actions.
... Most of the African coastline is too warm for laminarian kelps, but there are large and significant kelp forests in the Benguela upwelling region on the west coast of South Africa and Namibia, and smaller kelp forests (Laminaria ochroleuca) in northwest Africa (Rezzoum et al. 2017). Kelp forest ecosystems are economically extremely important where they occur (Blamey and Bolton 2018;Eger et al. 2023), and are being affected by climate change in many regions, with 38 % showing evidence of recent decline (Krumhansl et al. 2016). Kelps are 'ecosystem engineers', as they are dominant species which form the basis of the entire ecosystem, providing habitat and food for a high biodiversity of marine life. ...
... Kelp forests have a multitude of economic benefits and this ecosystem, in South Africa only, has an estimated value of US$ 434 million year −1 (currently ZAR 8.2 billion year −1 ), of which ca. US$ 290 million year −1 (ZAR 5.5 billion year −1 ) contributes to the South African gross domestic product (GDP), with ecotourism (almost 40 %), recreational fishing (28 %), and commercial and illegal fishing (ca. 15-16 % each) being the major contributors (Blamey and Bolton 2018). A minimum estimate of kelp biomass in South Africa was calculated by Anderson et al. (2007) at almost 600,000 tonnes fresh weight, with some areas not estimated and only surface kelp included. ...
The Benguela upwelling region on the west coast of South Africa/Namibia has the only major kelp forests on the African continent. South Africa has four species of laminarian kelps; Ecklonia maxima , Laminaria pallida dominate kelp forests in the west coast Benguela upwelling system, with Macrocystis pyrifera occurring rarely in this region and Ecklonia radiata largely confined to the more nutrient-poor south and east coasts. Growth studies on these species have been limited to laboratory experiments and very few initial, small-scale coastal studies. As in other Atlantic regions, there is growing interest in the potential for kelp aquaculture in Southern Africa, and recent pilot initiatives. A comprehensive summary of available literature on South African kelps, their biology and ecology, distribution and growth parameters, is presented, and the potential for kelp aquaculture discussed in relation to recent developments elsewhere on Atlantic and Eastern Pacific coastlines. Recommendations are made with respect to the choice of potential species and sites.
... Kelp forests have a multitude of economic benefits and this ecosystem, in South Africa only, has an estimated value of US$ 434 million year −1 (currently ZAR 6.6 billion year −1 ), of which c. US$ 290 million year −1 (ZAR 4.4 billion year -1 ) contributes to the South African gross domestic product (GDP), with ecotourism (almost 40%), recreational fishing (28%), and commercial and illegal fishing (c. 15-16% each) being the major contributors (Blamey and Bolton 2018). ...
... South African kelp forest ecosystems have been severely over-exploited by the fishing industry. The West Coast rock lobster biomass is estimated to be at <3% of pre-exploitation values with similar figures for the local abalone, and many linefish stocks are considered collapsed or over-exploited (Blamey and Bolton 2018). In contrast kelp harvesting has been a relatively minor and fairly well controlled industry. ...
This report entails the results of a 3-months study to establish the feasibility of kelp farming on South Africa's west Coast. Focus was on bio-physical environmental conditions, enabling and conflicting land and ocean use conditions, financial considerations and lab-based technical cultivation trials.
... Kelp forests provide a wide range of ecosystem goods and services with high economic value (e.g. Bennett et al. 2016, Blamey & Bolton 2018. As sessile, (mainly) low-dispersal species, kelps are sensitive to rapid changes in environmental conditions, rendering populations in several areas under threat due to ocean warming. ...
... In South Africa, it is 1 of 2 dominant kelp species to gether with E. maxima, while in Namibia it is the sole habitat-forming species (Rothman et al. 2017). L. pallida is an economically and ecologically valuable kelp species in African coastal waters (Critchley et al. 1991, Blamey & Bolton 2018. The distributional area of the species is characterised by strong upwelling and warm-temperate surface waters ranging from 11 to 22°C (Demarcq et al. 2003, https://meteonews.fr/en/Water_sports/ ...
ABSTRACT: As climate change threatens marine ecosystems, sessile species such as kelps can be particularly strongly impacted by rapidly changing conditions. In this context, phenotypic plasticity can allow organisms to optimize their performance to cope with high temperatures. Here, we investigated the effects of thermal history on reproductive success and cross-generational plasticity in the warm-temperate kelp Laminaria pallida. Our results show that warm temperature during the vegetative growth of gametophytes improved subsequent reproductive success under optimum compared to cold conditions. Cross-generational effects were evident; thermal tolerance of microscopic F1 sporophytes was modulated by the thermal history of the parental gametophytes. However, the effects were complex, varying by physiological trait, exposure time and genotype (crosses). A warm thermal history increased the photosynthetic efficiency of sporophytes at moderate to high temperatures, while the sporophytes from a cold thermal history grew more during the first 8 days at all experimental temperatures, but disappeared over time. Our results suggest that preconditioning for reproduction and cross-generational effects can play an important role in the adaptation of L. pallida to warm habitats, highlighting the importance of incorporating thermal history effects in physiological studies to accurately predict the vulnerability of populations and species to future warming climates.
... The economics of ecosystem services (ES) especially marine ecosystems is being extensively determined in a few European (Bermejo et al. 2022) countries like Sweden (Hasselström et al. 2018), Norway (Gundersen et al. 2021) and African and East Asian countries, South Africa (Blamey and Bolton 2018) and Korea (Park et al. 2021). Various methods have been employed to arrive at economic gains like Delphi technique. ...
... They are perceived as a critical resource against global warming and one major group of these photosynthetic organisms-seaweed, is no different. The estimates revealed that common seaweeds growing in temperate regions can fix more than 100,000 t of carbon year −1 in 5000 ha of kelp farms (Blamey and Bolton 2018). ...
For more than a billion years, seaweeds have been a segment of marine primary productivity this fact must be contemplated while considering emerging conceptual frameworks such as the "blue economy". This sector not only has the potential to provide renewable feedstock but its cultivation and processing ticks an important box for sustainable development. Seaweed cultivation in India is gaining momentum and great attention is being given to developing the infrastructure. A flagship program 'Pradhan Mantri Matsya Sampada Yojana (PMMSY)' has provided adequate budgetary allocation to achieve a production of 11.2 Mt (fresh) feedstock. However, the scheme seems to focus only on material benefits (product development) and the ecosystem services, especially regulatory services have seldom been taken into consideration. Thus, the present article tries to address the estimation of potential regulatory ecosystem services [capture carbon, uptake nutrients and heavy metals (Cr, Co, Cd)] met through Kappaphycus alvarezii farming, at the Pan-India level. The estimates were made for both tube net and raft cultivation methods separately. The farm cover was estimated to be around 700,000 ha supporting approximately 780,000 farmers for tube net, while it was 56,000 ha supporting ~ 1.25 million farmers for raft cultivation. A total number of tube nets that would be put to use would be 140 million and 56 million in the case of rafts. Once the target is achieved India would have gained the ability to annually capture approximately 600,000 t of carbon, 22,000 t of nitrogen, and 2000 t of phosphorous and absorb more than 1000 t of heavy metals cumulatively. Nevertheless, a monetary valuation of ecosystem services is needed to arrive at rational decisions by policy-makers and resource managers.
... The economics of ecosystem services (ES) especially marine ecosystems is being extensively determined in a few European (Bermejo et al. 2022) countries like Sweden (Hasselström et al. 2018), Norway (Gundersen et al. 2021) and African and East Asian countries, South Africa (Blamey and Bolton 2018) and Korea (Park et al. 2021). Various methods have been employed to arrive at economic gains like Delphi technique. ...
... They are perceived as a critical resource against global warming and one major group of these photosynthetic organisms-seaweed, is no different. The estimates revealed that common seaweeds growing in temperate regions can fix more than 100,000 t of carbon year −1 in 5000 ha of kelp farms (Blamey and Bolton 2018). ...
For more than a billion years, seaweeds have been a segment of marine primary productivity this fact must be contemplated while considering emerging conceptual frameworks such as the “blue economy”. This sector not only has the potential to provide renewable feedstock but its cultivation and processing ticks an important box for sustainable development. Seaweed cultivation in India is gaining momentum and great attention is being given to developing the infrastructure. A flagship program ‘Pradhan Mantri Matsya Sampada Yojana (PMMSY)’ has provided adequate budgetary allocation to achieve a production of 11.2 Mt (fresh) feedstock. However, the scheme seems to focus only on material benefits (product development) and the ecosystem services, especially regulatory services have seldom been taken into consideration. Thus, the present article tries to address the estimation of potential regulatory ecosystem services [capture carbon, uptake nutrients and heavy metals (Cr, Co, Cd)] met through Kappaphycus alvarezii farming, at the Pan-India level. The estimates were made for both tube net and raft cultivation methods separately. The farm cover was estimated to be around 700,000 ha supporting approximately 780,000 farmers for tube net, while it was 56,000 ha supporting ~ 1.25 million farmers for raft cultivation. A total number of tube nets that would be put to use would be 140 million and 56 million in the case of rafts. Once the target is achieved India would have gained the ability to annually capture approximately 600,000 t of carbon, 22,000 t of nitrogen, and 2000 t of phosphorous and absorb more than 1000 t of heavy metals cumulatively. Nevertheless, a monetary valuation of ecosystem services is needed to arrive at rational decisions by policy-makers and resource managers.
... harvest, fisheries, and tourism) have estimated regional kelp forests to be worth between $290 million (e.g. Ecklonia and Laminaria forests in South Africa) 30 and USD $540 million per year (e.g. Lessonia and Macrocystis forests in Central-Northern Chile) 12 . ...
... These genera are distributed across the Northern and Southern Pacific, Northern and Southern Atlantic, and parts of the Arctic and Southern Oceans, and encompass most of the global kelp distribution 10 . Within these genera we analysed three services that had market values reported: fisheries (i.e., secondary) production, carbon capture, and nutrient cycling, which past studies suggest comprise the most valuable market services provided by kelp forests 12,23,30 . ...
While marine kelp forests have provided valuable ecosystem services for millennia, the global ecological and economic value of those services is largely unresolved. Kelp forests are diminishing in many regions worldwide, and efforts to manage these ecosystems are hindered without accurate estimates of the value of the services that kelp forests provide to human societies. Here, we present a global estimate of the ecological and economic potential of three key ecosystem services - fisheries production, nutrient cycling, and carbon removal provided by six major forest forming kelp genera (Ecklonia, Laminaria, Lessonia, Macrocystis, Nereocystis, and Saccharina). Each of these genera creates a potential value of between 147,100/hectare each year. Collectively, they generate between 562 billion/year worldwide, with an average of 29,900, 904 Kg/Ha/year) and nitrogen removal ($73,800, 657 Kg N/Ha/year), though kelp forests are also estimated to sequester 4.91 megatons of carbon from the atmosphere/year highlighting their potential as blue carbon systems for climate change mitigation. These findings highlight the ecological and economic value of kelp forests to society and will facilitate better informed marine management and conservation decisions.
... Africa, e.g., provision of food ; water ; cultural values ; and an alternative and/or supplementary income . In addition, conservation and restoration activities can create much-needed jobs (Turpie et al., 2008), and so do entire industries depending on functioning EI like naturebased tourism (Biggs et al., 2011) and fisheries (Blamey and Bolton, 2018). The mapping and integration of EI in the coastal zone address four of the ten priority actions identified in the coastal component of the National Biodiversity Assessment (2018) to improve managing and conserving biodiversity: 1) restore the coast, 2) diversify and create more jobs, 3) effectively communicate the benefits of coastal biodiversity, and 4) address critical knowledge gaps (i.e., mapping and assessing EI; . ...
... The mapping and integration of EI in the coastal zone address four of the ten priority actions identified in the coastal component of the National Biodiversity Assessment (2018) to improve managing and conserving biodiversity: 1) restore the coast, 2) diversify and create more jobs, 3) effectively communicate the benefits of coastal biodiversity, and 4) address critical knowledge gaps (i.e., mapping and assessing EI; . In addition, EI strengthens South Africa's resilience in the face of climate change (Blamey and Bolton, 2018; in a cost-effective way (Rao et al., 2015). Finally, the benefits of EI conservation also contribute to international commitments made by South Africa, for example, the adoption of the Sustainable Development Goals in 2015 (SDGs; , and can likely contribute to the emerging post-2020 Biodiversity goals of the United Nations Convention on Biological Diversity. ...
... Kelp forests dominate along approximately one-third of the world's coastlines in polar/ subpolar and temperate latitudes in both hemispheres (Krumhansl et al., 2016;. Their diverse variety of habitat types delivers a broad range of valuable ecosystem services Blamey and Bolton, 2018;Eger et al., 2021a). ...
... Kelp forests have declined around the world and in some cases have nearly disappeared entirely from a region (Thibaut et al., 2005;Fujita, 2011;Johnson et al., 2011;Vasquez et al., 2014;Blamey and Bolton, 2018;Rogers-Bennett and Catton, 2019;Filbee-Dexter et al., 2020). The cause of these declines range from local stressors, such as pollution, to global impacts, particularly climate change . ...
Despite a relatively long history in places like Japan, Korea, and California, the science and practice of kelp forest restoration is still in its infancy, and there remains a wealth of knowledge to be learned and shared from our collective failures and successes. To date, many projects have remained disconnected and had limited opportunities to share their experiences and learnings. The practice of kelp forest restoration will be greatly enhanced with collaborative, science-based efforts, where all stakeholders and custodians are engaged in decision-making and even short-term failures can yield insights that contribute to longer-term success.
The development of the Kelp Restoration Guidebook was informed by a series of global workshops, and an expert panel of authors and editors, with the aim to share and distil lessons learned from kelp restoration efforts globally. The intent is for this guidebook to serve as a starting point for practitioners, researchers, managers, and custodians to learn about the steps of restoration and access an active community of practice—all to improve the likelihood of success for future restoration projects. The broad lessons contained herein can then be extended and refined to suit local kelp species and circumstances. Ultimately, by cultivating an alliance of kelp forest restoration practitioners around the world, we can work together to ensure that kelp forests flourish in our planet’s changing seas.
... S. japonica exhibits a heteromorphic alternation of generations, comprising the sporophyte generation of multicellular thallus and gametophyte generation of unicellular and uniseriate cell filaments, making it valuable for studying the evolution of multicellular algae. As the principal species in worldwide aquaculture, with an annual production of 10,861 kilotons, accounting for 29.75% of global aquatic plant aquaculture (FAO, 2022), it is extensively utilized across various sectors, including food, medicine, feed, and other industries [2,3]. In recent years, scientific research has demonstrated that kelp farming has the potential to absorb significant quantities of carbon dioxide, thereby creating a carbon sink effect that can contribute to the mitigation of ocean acidification resulting from global climate change [4,5]. ...
Saccharina japonica is one of the most productive aquatic plants in the world, widely used in food, feed, medicine, and other industries. Predominantly inhabiting temperate marine environments in mid- to high-latitude regions of the Northern Hemisphere, the growth of S. japonica is significantly limited by high-temperature stress. Abscisic acid (ABA) plays an important role in plant growth and development and stress responses. However, the role of ABA on high-temperature stress tolerance in S. japonica still needs to be further elucidated. Here, we found that exogenous ABA significantly alleviated disease and decay in S. japonica under high-temperature stress while also increasing the relative growth rate, chlorophyll fluorescence parameters, photosynthetic pigment, and osmotic substance content. Meanwhile, exogenous ABA enhanced the activity of protective enzymes and up-regulated the transcript levels of antioxidant-related genes, thereby reducing oxidative damage. Most importantly, we observed a significant increase in ABA content and the transcript levels of key genes involved in ABA synthesis in S. japonica under high-temperature stress, which were further amplified by the addition of exogenous ABA. In conclusion, this study provides evidence that ABA can moderate the detrimental effects of high-temperature stress and provides a theoretical basis for the screening of S. japonica germplasm resources and the cultivation of new stress-resistant varieties.
... The Cape Town peninsula is surrounded by the Table Mountain National Park Marine Protected Area where most kelp forests are located; here, conservation and monitoring are required for species living in help forests (Sowman & Sunde, 2018). Kelp forests not only provide habitat to species but also other ecosystem services like food, coastal protection, and recreation; their monitoring and preservation are thus important (Blamey & Bolton, 2018;Steneck & Johnson, 2014;Teagle et al., 2017). ...
Participation of marine tourists in scientific activities or Citizen Science can be considered a way to promote tourism that is educational, enriching, and valuable to the achievement of Sustainable Development Goals among other objectives set by the United Nations Ocean Decade. Whether tourists’ experiences result in positive outcomes, however, requires continuous investigation. This study assessed the short-term impacts of marine tourists’ participation in scientific activities, with a focus on experiential and reflective engagement and individual learning outcomes, and the potential influence of the former on the latter. A total of 111 tourists participated in a questionnaire survey following an experience of snorkeling/diving with a scientist to monitor the kelp forests of Cape Town during 2021‐2022. The results of the survey showed positive impacts of the scientific experience on tourists. In particular, experiential and reflective engagement significantly positively influenced specific individual learning outcomes. These findings emphasize the importance of designing marine scientific tourism experiences that are engaging to improve learning and result in positive behavioral intentions to partake in similar activities in future while supporting more sustainable forms of tourism.
... Due to kelps' ecological role in the nearshore, they are regarded as ecological engineers as well as important influencers of biodiversity along temperate shorelines (Fowler-Walker et al. 2005; Smale and Moore 2017; Wernberg and Goldberg 2008). Kelps are also important from a socio-economic perspective, as they provide habitats for economically important species such as abalone and rock lobster (Blamey and Bolton 2018;Vásquez et al. 2014) and are harvested for various uses, ranging from feed for the aquaculture sector to pharmaceuticals (Smit 2004;Troell et al. 2006). ...
Kelps are resilient organisms, capable of thriving in high-energy wave environments. However, when hydrodynamic drag forces exerted by the wave environment exceed the kelps’ structural limits, individuals become dislodged. Floating kelps generally follow ocean currents, traveling long distances until air-filled structures fail or the epibiont load becomes too great, causing them to sink to the seafloor. The ability of kelp to disperse over vast offshore and nearshore systems makes them important for organic subsidy and as a dispersal vector for marine organisms. Previous research on dislodged macroalgae focused on context-specific rafts, limiting insights into the broader ecological role of floating kelp. This study employed a site-specific Lagrangian trajectory model to describe the spatial distribution of floating Ecklonia maxima along the South African coastline. The model incorporated buoyancy and sinking using site-specific morphological data. Findings revealed that the distribution of floating E. maxima is influenced by oceanographic conditions, and seasonal patterns were also evident. Mesoscale features played a vital role in kelp accumulation on the surface and seafloor and acted as barriers to dispersal. This study offers essential insights into kelp’s role as an organic subsidy and provides numerical evidence for kelp’s potential as a carbon sink, contributing to a better understanding of kelp ecosystems and their ecological functions.
... In addition to direct habitat provisioning, large macroalgae alter local environmental conditions and influence resource availability and, as such, marine forests are widely recognised as hotspots of biodiversity and productivity (Steneck et al., 2002;Pessarrodona et al., 2022;UN, 2023). These forests also underpin wider ecosystem services, such as habitat provisioning for commercially important fisheries species and nutrient cycling, which have significant socioeconomic benefits to human societies (Bennett et al., 2015;Blamey and Bolton, 2018;Eger et al., 2023;UN, 2023). ...
We examined spatiotemporal variability in the structure of faunal assemblages associated with the warm-temperate pseudo-kelp Saccorhiza polyschides towards its range centre (Western English Channel, southwest UK), to better understand its role as a habitat-former in the northeast Atlantic. A total of 180 sporophytes and their associated fauna were sampled across three months, three sites, and two depths. Assemblage abundance and biomass varied markedly between three morpho-functional sporophyte components (i.e., holdfast, stipe, blade). We recorded rich and abundant macroinvertebrate assemblages, comprising nine phyla, 28 coarse taxonomic groups, and 57 species of molluscs, which consistently dominated assemblages. We observed pronounced seasonality in faunal assemblage structure, marked variability between sites and depths, and strong positive relationships between biogenic habitat availability and faunal abundance/biomass. S. polyschides sporophytes are short-lived and offer temporary, less-stable habitat compared with dominant perennial Laminaria species, so shifts in the relative abundances of habitat-formers will likely alter local biodiversity patterns.
... In South Africa, kelp forests occur over approximately 1000 km of coastline in the southern portion of the Benguela Current Large Marine Ecosystem (Blamey and Bolton 2018). The common kelp species in this region, specifically along the western Cape coast, include Ecklonia maxima ('sea bamboo'), Laminaria pallida ('split-fan kelp') and Macrocystis pyrifera ('bladder kelp') (Maneveldt 2011;Maneveldt and Frans 2001). ...
In an era of climate change, South Africa’s kelp forests offer important opportunities for sustainable resource utilization. However, these opportunities also bring risks of over-exploitation. The mismanagement of kelp forests through monistic and exclusionary strategies must therefore be avoided. Emphasizing the value of plural knowledges and cultural norms associated with kelp, here we advocate for inclusive and integrated marine resource management to ensure the resilience of South Africa’s kelp forests and the well-being of coastal communities that depend on them.
... These questions are highly relevant for the southeastern Atlantic Laminaria pallida (Greville), a kelp that is distributed throughout the southwestern coast of Africa from northern Namibia to southern South Africa (Assis et al., 2022), and which provides a variety of ecosystem services of economic and ecological value (Critchley et al., 1991;Blamey & Bolton, 2018). In this species, we have identified variant male strains derived from one sporophyte, which form egg-like structures and sporophytes under gametogenic conditions, although showing morphological features typical of a male. ...
... In contrast to other marine ecosystems, including kelp systems elsewhere that are experiencing declines 8 , the Great African Seaforest is extending its range eastwards 5 , due to cooling environments on the west and south-west coast. Nonetheless, kelp forests in South Africa are increasingly exposed to the impacts of anthropogenic pressures 9 , threatening their long-term persistence and ecosystem services, that have been estimated at 5 billion rand (ZAR) per year 10 . Although South African kelpforest associated biodiversity was extensively studied from the 1970s until the late 2000s 6,7,11,12 , there is great potential for marine biodiversity research in South Africa due to the anticipated large numbers of undiscovered species 7,13 . ...
Environmental DNA (eDNA) metabarcoding is a promising tool for monitoring marine biodiversity, but remains underutilised in Africa. In this study, we evaluated the ability of aquatic eDNA metabarcoding as a tool for detecting biodiversity associated with a South African kelp forest, an ecosystem that harbours high diversity of species, many of which are endemic, but are also sensitive to changing environmental conditions and anthropogenic pressures. Using fine-scale spatial (1 m and 8 m) and temporal (every four hours for 24 h) sampling of aquatic environmental DNA and targeting two gene regions (mtDNA COI and 12S rRNA), metabarcoding detected 880 OTUs representing 75 families in the broader metazoan community with 44 OTUs representing 24 fish families. We show extensive variability in the eDNA signal across space and time and did not recover significant spatio-temporal structure in OTU richness and community assemblages. Metabarcoding detected a broad range of taxonomic groups, including arthropods, ascidians, cnidarians, echinoderms, ctenophores, molluscs, polychaetes, ichthyofauna and sponges, as well as Placozoa, previously not reported from South Africa. Fewer than 3% of OTUs could be identified to species level using available databases (COI = 19 OTUs, 12S = 11 OTUs). Our study emphasizes that kelp-forest associated biodiversity in South Africa is understudied, but that with careful consideration for sampling design in combination with increased barcoding efforts and the construction of regional databases, eDNA metabarcoding will become a powerful biomonitoring tool of kelp-forest associated biodiversity.
... including exploited species, and are a proxy for wider species richness (Christie et al., 2003;Blamey and Bolton, 2018). The diversity of rocky reef fish has also been shown to be indicative of increased small-scale structural complexity, biological cover, and reef substrate, features that typically result in higher species richness across trophic structures (Parsons et al., 2016). ...
Aotearoa (New Zealand) is a global hotspot of marine biodiversity and has a productive commercial fishing industry. Despite the importance of sustainably managing biodiversity to support fisheries, less than 1% of Aotearoa's Exclusive Economic Zone (EEZ) is protected in marine reserves, and Benthic Protection Areas, which cover 28% of the EEZ, are inefficiently placed, providing limited biodiversity and fisheries benefits. Here, we provide a spatial analysis of the Aotearoa EEZ, determining optimal areas that balance marine conservation with the minimal displacement of fishing. We define the minimum length of a big old fat fecund female fish (BOFFFF) for three commercially important exploited species, and use boosted regression trees to determine areas of high reproductive potential. Model results were then used to incorporate reproductive potential into systematic conservation planning. We used the decision-support software Zonation to consider the distribution of threatened species hotspots, biodiversity, and BOFFFFs against fishing catch (all commercially exploited species) and high-value fisheries (10 commercially exploited species) to determine priority areas for marine protection. Results showed that threatened species, biodiversity, and areas with high reproductive potential could be conserved with little impact on fishing catch (86% maintained) and value (87% maintained), though high-value fisheries were found to have greater overlap with biodiversity. Our research indicates that trade-offs with fisheries need not impede the designation of protected areas required to achieve conservation and fisheries sustainability goals.
... This fact makes kelp forests among the most important marine biomes on the planet (Jayathilake and Costello 2021; Duarte et al. 2022). Across this distribution, kelp forests are ecosystems of high regional importance (Buschmann et al. 2014;Bennett et al. 2016;Blamey and Bolton 2018) and based on three services, fisheries production, carbon cycling, and nutrient cycling, have an annual economic value of 500 billion US$ (Eger et al. 2023). Beyond economic impacts, kelp forests have important cultural significance (Dillehay et al. 2008;Thurstan et al. 2018), are used in art , form the basis of myths and lore (O'Connor 2017;Pérez-Lloréns et al. 2020), are places where people can interact with the ocean and thus have their own intrinsic value (Lucrezi 2021). ...
Marine kelp forests cover 1/3 of our world's coastlines, are heralded as a nature-based solution to address socio-environmental issues, connect hundreds of millions of people with the ocean, and support a rich web of biodiversity throughout our oceans. But they are increasingly threatened with some areas reporting over 90% declines in kelp forest cover in living memory. Despite their importance and the threats they face, kelp forests are entirely absent from the international conservation dialogue. No international laws, policies, or targets focus on kelp forests and very few countries consider them in their national policy. The Kelp Forest Challenge addresses that gap. Together with 252 kelp experts, professionals, and citizens from 25 countries, the Kelp Forest Challenge was developed as a grassroots vision of what the world can achieve for kelp forest conservation. It is a global call to restore 1 million and protect 3 million hectares of kelp forests by 2040. This is a monumental challenge, that will require coordination across multiple levels of society and the mobilization of immense resources. Pledges may therefore include area for protection or restoration, enabling pledges which assist in conservation (funding, equipment, professional expertise, capacity building), or awareness-based pledges which increase awareness or education about kelp forests. Correspondingly, participants may be from government, scientific institutions, private sector, NGOs, community groups, or individuals. This challenge is the beginning of a 17-year mission to save our kelp forests and anyone and any organisation is invited to participate.
... It also forms EI that provides a plethora of ecosystem services. These services provide many benefits to South Africans (Harris et al., 2019b) and make substantial contributions to the economy, e.g., through tourism (Lewis et al., 2012;Rogerson and Rogerson, 2020) and fishing (Blamey and Bolton, 2018). ...
... Rather, the few valuations that exist adopt an economic standpoint, following a monistic approach that does not incorporate the plurality of value dimensions, or place these within the context of local users. For instance, Blamey and Bolton (2018) undertook an economic valuation of kelp forests in South Africa, estimating their value to be US$434 million, US$144 million of which was attributed to indirect ecosystem services such as nutrient cycling, carbon fixation, and coastal protection. However, this study did not consider facets of non-use and non-market value such as the intrinsic, bequest, and cultural value of kelp. ...
Kelp are large seaweeds that provide a variety of contributions to humans and the environment. In South Africa, kelp forests are expanding as a consequence of climate change. Considering this expansion, assessing local perceptions and values around kelp’s contributions may assist with the implementation of inclusive management strategies. The lack of consideration of non-market and non-use values is a gap in kelp valuation studies, with kelp ecosystems and their use rarely valued outside of classical economic valuation frameworks. This study sought to fill this research gap, intending to assess local perceptions about varied value dimensions associated with kelp using a pluralistic valuation approach. Drawing from a sample population of Recreational Users and/or Coastal Community Members, Environmental Managers and Conservationists, and Kelp and/or Abalone Industry, the study investigated perceptions of value towards kelp in the Western Cape region of South Africa. Results indicate that the perceived value of kelp extends far beyond its economic value as a harvested resource. Rather, individuals highly value kelp’s ecological and social contributions, and have strong relational values towards kelp, recognizing its role in enhancing their quality of life and well-being. While most individuals did not display significant negative perceptions around kelp, some individuals in the Kelp and/or Abalone Industry indicated frustrations with kelp management strategies and kelp concession permit allocation processes. These findings highlight the need to incorporate local perceptions in integrated marine resource management solutions that recognize the plurality of values not only around kelp in the Western Cape but marine biodiversity at large.
... Social and economic effects. This intervention could benefit fisheries and ecotourism, as seaweed beds can be important nurseries for sport and commercial target species and many are attractive dive tourism locations [119,12,34]. However, it could also have negative impacts on short-term fishery revenues in contexts which require reductions in fishing pressure to restore predator populations capable of regulating grazing pressure, if that is what is needed to restore a seaweed stand. ...
There is an urgent need to achieve the United Nations Sustainable Development Goals (SDGs). At the same time, greenhouse gasses (GHGs) that contribute to global warming must be reduced to avoid even more severe climate disruption. Macroalgal (seaweed) systems can help the world achieve the SDGs by producing food, other valuable products, livelihoods, and a number of ecological benefits. Seaweed systems may also be drawing down atmospheric carbon dioxide, an important GHG, under some conditions. However, the net impacts of seaweed systems on GHGs (“blue carbon”) depends on many context-specific, complex biogeochemical processes and have thus far been difficult to quantify. We engaged experts in a system mapping exercise to support decision-making in the context of the high levels of uncertainty associated with seaweed blue carbon. The conservation and restoration of seaweed stands appears to be a low-regrets intervention that would produce many benefits, including some carbon sequestration under some conditions, with low risk. Increasing the productivity of seaweed farms may have a similar benefit and risk profile. A large expansion of seaweed farming coupled with sinking the seaweed biomass could significantly increase carbon sequestration, but with relatively large social, economic, and ecological risks. Certain products made from seaweed that sequester carbon, replace GHG-intensive products, or suppress GHG emissions could enhance the climate and socioeconomic benefits of seaweed systems while also improving prospects for quantifying and verifying them. More research and interventions will likely be necessary for such products to scale. A portfolio of seaweed systems would probably be necessary to realize the variety of benefits that these systems are capable of generating.
... Similarly, macroalgal forests provide a variety of ecological services, including direct support for commercial, recreational, and subsistence fisheries and aquaculture [28,30,31,36]. Erosion management and temperature change are examples of indirect ecological services. ...
The ecosystem services can be divided using two major classification systems, the Millennium Ecosystem Assessment (MEA) and the Common International Classification of Ecosystem Services (CICES). In the MEA system, the ecosystem services are divided into four major service clusters: supporting, provisioning, regulating, and cultural. On the other hand, the CICES system regards the "MEA supporting services" as organism natural function (and not an ecosystem service). Thus, this function is the basis for all the three CICES ecosystem services (provisioning, regulating, and cultural) provided by one organism. These ecosystem services can be analyzed for the type of habitat, fauna or flora. Seaweeds, or marine macroalgae, are one of the key organisms in estuarine and seawater habitats ecosystems, which currently is of extreme importance due to the climate changes and the blue-green economy. Seaweeds and humankind have been interlinked from the beginning, mainly as a food source, fibers, biochemicals, natural medicine, ornamental resources, art inspiration, and esthetic values in several coastal communities. Moreover, currently they are being studied as green carbon, carbon sequestration, and as a possible source for the biomedical and pharmaceutical areas. This review is a concise review of all ecological services provided by seaweeds and their impact in the human life and maintenance of the ecosystem status quo. The future of seaweeds use is also approached, regarding the promotion of seaweed ecological services and its dangers in the future.
... Many kelp species also carry significant economic value, supporting aquaculture and direct harvest industries, commercial and recreational fisheries, and tourism Blamey & Bolton, 2018;Costanza et al., 2014;Vásquez et al., 2013). However, kelps around the world are showing signs of decline due to a variety of human impacts, including climate change, posing a direct threat to the integrity of marine ecosystems and associated socio-economic values (Krumhansl et al., 2016;Phelps et al., 2017;Wernberg et al., 2010). ...
Aim
Kelp forests throughout temperate regions of the world serve as foundation species that play a critical role in sustaining the health and function of marine ecosystems but are experiencing declines in abundance due to a loss in resilience as the ocean climate changes. Ocean warming along southeast Australia has already been linked to dramatic losses of kelp species and is contributing to the range expansion and population increases of two species of sea urchin. This research attempts to understand the impact of multiple stressors on the decline in kelps in this region.
Location
Coastal Waters of Victoria, Southeast Australia.
Methods
In this study, we use long‐term (>20 years) datasets on biological observations across Victorian waters to determine trends in coverage and the impact of multiple environmental variables (oceanography, habitat, and urchin abundances) on two important kelps that serve as foundation species (Phyllospora comosa and Ecklonia radiata) using boosted regression trees. These models were then used to develop predictive distribution models for each species and also to project abundance distributions into the future.
Results
We found that both kelp species are decreasing in percent coverage over time with multiple environmental variables contributing to these declines, including increasing temperatures, intensifying wave energy, changes in currents and recruitment patterns, and increases in urchin populations. Additionally, future projections of temperature, wave energy, and urchin populations show that both species will continue to decrease across 62%–94% of their range by 2090.
Main conclusions
Long‐term biological datasets allowed us to develop maps of the past, current, and future distributions of these important foundation species, providing valuable information to managers for prioritization of areas for targeted urchin management and restoration of kelps. Understanding the environmental factors affecting their distribution helps guide manager restoration investments in regions where kelp populations are most likely to persist in the future.
... Kelp forests around the world support economic inputs, i.e., the value of kelp in South Africa is estimated at USD 434 million per year [67], and in the Falkland Islands at USD 342 billion per year [29]. The southeastern Pacific region's kelp forests are dominated by M. pyrifera and their value in terms of ES has been evaluated at USD 811,000 per kilometer per year [22]. ...
Marine ecosystems such as kelp are gaining recognition for providing ecosystem services (ES) along the coastal regions worldwide. Here, we synthesize information from the last four decades of research on the structure, functioning and threats of kelp forests, and the ES they provide in the Humboldt Current System (HCS) where information is scarce. The SALSA (Search, Appraisal, Synthesis and Analysis) framework was used for the literature survey and review. From 86 selected articles, only 4 directly discussed kelp ES in Chile. Supporting services-related articles were the most prevalent (n = 59), followed by provisioning (n = 19), regulating (n = 3) and cultural services (n = 1). ES-related research was mostly conducted in Chile (n = 77). Studies in Peru (n = 5), and in Chile and Peru at same time (n = 4) were scarce. Our search also showed that Lessonia trabeculata presented the highest number of associated taxa (n = 213), followed closely by M. pyrifera (n = 210). However, the number of phyla reported was higher in M. pyrifera (n = 17) than in the Lessonia species (n = 7-13). Natural and anthropic impacts on the biodiversity of kelp forests using novel technologies would facilitate the quantitative study and economic valuations of the services provided by these ecosystems at the Humboldt Current System.
... Depending on a country of kelp source, 1 km 2 of kelp can be worth from USD 500 000 (South Africa) to USD 800 000 (Chile), and to USD 1 000 000 (Australia). These numbers refer to the market price of kelp as food and as raw material for the extraction of its natural compounds, as well as its ecological value as habitat provision, shelter and direct food for marine species, coastal protection and carbon storage Vásquez et al., 2014;Bennett et al., 2016;Blamey and Bolton, 2018). However, this monetary tag of kelp goods and services is very likely to be underestimated due to the lack of in-depth studies. ...
The most important marine coastal ecosystem in the Chilean coast are kelp forests. This review is based on ecological studies regarding different aspects of subtidal kelp ecosystems along the Chilean coast. It highlights the most interesting findings in (1) biology of subtidal kelp in Chile, with particular reference to (2) habitats formed by kelp, and considered the successful examples and promising results in the (3) kelp as an industrial resource (Biotechnological approach of kelps and aquaculture). The impact caused by (4) El Niño-Southern Oscillation (ENSO) is discussed as an important climatic event that could help to forecast the future of the kelp ecosystem. In addition, this literature review outlines the knowledge gaps on subtidal kelp along the South East Pacific Coast of Chile, so that research can be strengthened in the future. Citation: Laukaityte Simona, Riera Rodrigo. 2022. The status of research and utilisation on the subtidal kelp along the Chilean coast: A literature review.
... Kelp forests are created by large habitat-forming brown macroalgae predominantly from the order Laminariales and extend over approximately 25% of the world's temperate and polar coastline (Wernberg et al., 2019b). Kelps are foundation species that support local biodiversity (Norderhaug et al., 2005;Teagle et al., 2017) and provide critical ecosystem services to human societies (Smale et al., 2013;Bennett et al., 2016;Blamey and Bolton, 2018) that are worth billions of USD year -1 (Eger et al., 2021). Long-term monitoring programs (> 20 years) show that 40% to 60% of the global kelp forests are declining (Krumhansl et al., 2016;Wernberg et al., 2019b). ...
Kelp forests are experiencing substantial declines due to climate change, particularly ocean warming and marine heatwaves, and active interventions are necessary to halt this decline. A new restoration approach termed “green gravel” has shown promise as a tool to combat kelp forest loss. In this approach, substrata (i.e. small gravel) are seeded with kelp propagules, reared in controlled conditions in the laboratory before out-planting to degraded reefs. Here, we tested the feasibility of cultivating Australia’s dominant kelp, Ecklonia radiata on green gravel with the aim of optimising the seeding conditions for E.radiata. We seeded substrata (i.e. gravel), that had different surface texture and size, with E. radiata gametophytes at two average seeding densities: high density of ~230 fragments mL⁻¹ and low density of ~115 fragments mL⁻¹. The tested substrata were small basalt, large basalt, crushed laterite and limestone. Gametophytes successfully adhered to all four tested substrata, however, gametophytes that adhered to the limestone gravel (the natural reef type off Western Australia) suffered extreme tissue bleaching likely due to dissolution and decrease in seawater pH. Gametophytes that adhered to the three other test substrata were healthy, fertilised following seeding and microscopic sporophytes were observed attaching to the gravel. Substrata and seeding density did not affect sporophyte growth (i.e. length) at the time of transferring into aquarium tanks (after three months of rearing in incubators) but over time substrata showed a significant effect on maximum lengths. After 12 months in aquarium tanks, sporophytes on both small and large basalt gravel were significantly larger than those on the crushed laterite. Gametophytes were also found to not only survive on the gravel itself but also detach from the gravel, settle successfully, fertilise and develop into healthy sporophytes ex situ on the surrounding substratum through lateral transfer. Substrata had a significant effect on density of detached gametophytes with rougher and larger gravel showing higher densities of detachment. Our results show the potential for green gravel to be a vector of dispersal for restoration in Western Australia where natural recovery of kelp forests has failed.
... Kelp forests are among some of the most productive systems on earth (Mann, 1973;Vilalta-Navas et al., 2018) and are essential in supporting other coastal and open ocean pelagic systems through detrital export (Duggins et al., 1989;Hobday, 2000a;Hobday, 2000b;Krumhansl and Scheibling, 2012). Their ecological (Bertocci et al., 2015;Blamey and Bolton, 2018) and economic (Chung et al., 2011;FAO, 2018) importance make them a key target group for conservation. As coastal ecosystems, kelp forests are exposed to a variety of anthropogenic and natural stressors that are both regional (pollution, invasive species, sedimentation, harvesting, fishing, storm surges, disease, herbivory and gene pollution from aquaculture) and global (climate change, El Niño Southern Oscillation) (Steneck et al., 2002;Schiel and Foster, 2015;. ...
Given the impacts of climate change and other anthropogenic stressors on marine systems, there is a need to accurately predict how species respond to changing environments and disturbance regimes. The use of genetic tools to monitor temporal trends in populations gives ecologists the ability to estimate changes in genetic diversity and effective population size that may be undetectable by traditional census methods. Although multiple studies have used temporal genetic analysis, they usually involve commercially important species, and rarely sample before and after disturbance. In this study, we run a temporal analysis of giant kelp, Macrocystis pyrifera, genetic diversity over the scope of 10 years (2008-2018) using the same microsatellite marker panel to assess the genetic consequences of disturbance in several populations of giant kelp (Macrocystis pyrifera) in the Southern California Bight. The study is a rare pre- and post-disturbance microsatellite analysis that included declines to giant kelp caused by the 2015/16 El Nino Southern Oscillation event. We used canopy biomass estimated by remote sensing (Landsat) to quantify the extent of disturbance to kelp beds, and sea surface temperature data to understand how kelp was pushed towards its temperature limits during this period. Despite prolonged periods with decreased canopy at several sites, no changes in genetic structure and allelic richness were observed. We argue that giant kelp in the region is best described as a “patchy population” system where true extinctions are rare. We discuss how deep refugia of subsurface sporophytes and cryptic microscopic life stages could have kept genetic diversity through disturbance. Given the increasing effects of climate change and uncertainty in modeling impacts of species with cryptic life history stages, we suggest further investigation to reveal the role such stages play in species resilience. Genetic monitoring studies of sites selected by remote census demographic and climate surveys should be continued in the future given the predicted impacts of climate change.
... Kelp forests are an iconic feature of the Atlantic coast of South Africa, where they play a key ecological role, protecting the coastline from wave action, supporting a rich and diverse biota, and hosting several economically important fisheries stocks, including rock lobsters, abalone and linefish (fish captured using hook and line), as well as the kelps themselves. For a recent general review of the ecology of kelp forests in the region see Branch and Branch (2018), and for a review of resources associated with South African kelp forests and their economic value see Blamey and Bolton (2018), who estimate the value of South Africa's kelp forest ecosystems at US$434 million year −1 (R5.8 billion year −1 ). ...
The recently described amphipod Sunamphitoe roberta lives only on the kelp Ecklonia maxima, where it excavates slit-like burrows along the distal margins of thicker primary fronds. Oval chambers along the bases of these slits may represent feeding areas. As burrowing proceeds, the damage progressively erodes back the frond margins, giving them characteristic attenuated and irregular profiles, and probably impacting secondary frond survival and growth, and hence kelp productivity. A kelp forest in False Bay, South Africa, was surveyed to determine what proportion of kelp was infected as well as which individuals were selected as hosts. Forty kelp heads were also dissected to ascertain numbers of amphipods per host and their size composition, and to document details of burrow structure. Of 305 adult kelps inspected, 117 (38.4%) showed visible amphipod damage. Rate of infestation was not correlated with stipe length but was positively correlated with head circumference and negatively correlated with the proportion of secondary fronds remaining. The 40 kelp heads dissected contained 786 S. roberta specimens. These comprised 154 adults (>8 mm), including 33 ovigerous females, and 632 juveniles (<8 mm). The number of amphipods per host ranged from 1 to 112 (mean 19.7 [SD 25.1]). Size distribution was bimodal, and the largest individual measured 20 mm.
... Kelp forests are complex, biodiverse, and highly productive ecosystems that occur globally between warm-temperate and polar regions (Teagle et al., 2017), and in deep tropical waters (Graham et al., 2007). Even though they provide important ecosystem services, their socio-economic value is only starting to be recognized (e.g., Vaśquez et al., 2014;Blamey and Bolton, 2018;Eger et al., 2021). Kelp forests benefit humankind directly (e.g., kelp harvesting, fishing, tourism), indirectly (e.g., habitat provision, climate regulation, nutrient cycling, carbon capture), and through cultural and spiritual value itself (biodiversity, recreation, science; Filbee-Dexter and . ...
Kelp forests in the North Atlantic are at risk of decline at their warm temperature distribution margins due to anthropogenic temperature rise and more frequent marine heat waves. To investigate the thermal adaptation of the cold-temperate kelp Laminaria digitata, we sampled six populations, from the Arctic to Brittany (Spitsbergen, Tromsø, Bodø [all Norway], Helgoland [Germany], Roscoff and Quiberon [both France]), across the species’ entire distribution range, spanning 31.5° latitude and 12-13°C difference in mean summer sea surface temperature. We used pooled vegetative gametophytes derived from several sporophytes to approximate the genetic diversity of each location. Gametophytes were exposed to (sub-) lethal high (20-25°C) and (sub-) optimal low (0-15°C) temperature gradients in two full-factorial, common-garden experiments, subjecting subsets of populations from different origins to the same conditions. We assessed survival of gametophytes, their ability to develop microscopic sporophytes, and subsequent growth. We hypothesized that the thermal performance of gametophytes and microscopic sporophytes corresponds to their local long-term thermal history. Integrated gametophyte survival revealed a uniform upper survival temperature (UST) of 24°C among five tested populations (Tromsø to Quiberon). In contrast, following two weeks of thermal priming of gametophytes at 20-22°C, sporophyte formation at 15°C was significantly higher in southern populations (Quiberon and Roscoff) compared to the high-latitude population of Tromsø. Between 0-15°C, survival of the Arctic population (Spitsbergen) was negatively correlated with increasing temperatures, while the southern-most population (Quiberon) showed the opposite. Thus, responses of survival at low, and sporophyte formation at high temperatures, support the concept of local adaption. On the other hand, sporophyte formation between 0-15°C peaked at 6-9°C in the Quiberon and at 9-12°C in the Spitsbergen population. Sporophyte growth rates (GR) both in length and width were similar for Spitsbergen, Tromsø and Quiberon; all had maximum GRs at 12-15°C and low GRs at 0-6°C. Therefore, responses of sporophyte formation and growth at low temperatures do not reflect ecotypic adaptation. We conclude that L. digitata populations display trait-dependent adaptation, partly corresponding to their local temperature histories and partly manifesting uniform or unpredictable responses. This suggests differential selection pressures on the ontogenetic development of kelps such as L. digitata.
... The high production of macroalgal forests supports food webs locally as well as at distant sites receiving their exported production (Krumhansl & Scheibling, 2012;Pessarrodona et al., 2018;Queirós et al., 2019). Food webs in macroalgal-dominated systems support highly productive commercial and recreational coastal fisheries (Bennett et al., 2016;Blamey & Bolton, 2018;Melis et al., 2019) The intense photosynthetic activity and attenuation of solar radiation by algal forests provide local refugia to vulnerable biota from elevated UV radiation and ocean acidification Wahl et al., 2018) and, in the case of intertidal fucoid canopies, from daily thermal extremes (Bulleri et al., 2018). Moreover, local reduction of currents by algal canopies protects shores from erosion and increases the local retention of organic matter (Estes & Palmisano, 1974;Løvås & Tørum, 2001). ...
Aim
Macroalgal habitats are believed to be the most extensive and productive of all coastal vegetated ecosystems. In stark contrast to the growing attention on their contribution to carbon export and sequestration, understanding of their global extent and production is limited and these have remained poorly assessed for decades. Here we report a first data-driven assessment of the global extent and production of macroalgal habitats based on modelled and observed distributions and net primary production (NPP) across habitat types.
Location
Global coastal ocean.
Time period
Contemporary.
Major taxa studied
Macroalgae.
Methods
Here we apply a comprehensive niche model to generate an improved global map of potential macroalgal distribution, constrained by incident light on the seafloor and substrate type. We compiled areal net primary production (NPP) rates across macroalgal habitats from the literature and combined this with our estimates of the global extent of these habitats to calculate global macroalgal NPP.
Results
We show that macroalgal forests are a major biome with a global area of 6.06–7.22 million km2, dominated by red algae, and NPP of 1.32 Pg C/year, dominated by brown algae.
Main conclusions
The global macroalgal biome is comparable, in area and NPP, to the Amazon forest, but is globally distributed as a thin strip around shorelines. Macroalgae are expanding in polar, subpolar and tropical areas, where their potential extent is also largest, likely increasing the overall contribution of algal forests to global carbon sequestration.
The southern coast of Africa is one of the few places in the world where water temperatures are predicted to cool in the future. This endemism-rich coastline is home to two sister species of kelps of the genus Ecklonia maxima and Ecklonia radiata, each associated with specific thermal niches, and occuring primarily on opposite sides of the southern tip of Africa. Historical distribution records indicate that E. maxima has recently shifted its distribution ~ 70 km eastward, to sites where only E. radiata was previously reported. The contact of sister species with contrasting thermal affinities and the occurrence of mixed morphologies raised the hypothesis that hybridization might be occurring in this contact zone. Here we describe the genetic structure of the genus Ecklonia along the southern coast of Africa and investigate potential hybridization and cryptic diversity using a combination of nuclear microsatellites and mitochondrial markers. We found that both species have geographically discrete genetic clusters, consistent with expected phylogeographic breaks along this coastline. In addition, depth-isolated populations were found to harbor unique genetic diversity, including a third Ecklonia lineage. Mito-nuclear discordance and high genetic divergence in the contact zones suggest multiple hybridization events between Ecklonia species. Discordance between morphological and molecular identification suggests the potential influence of abiotic factors leading to convergent phenotypes in the contact zones. Our results highlight an example of cryptic diversity and hybridization driven by contact between two closely related keystone species with contrasting thermal affinities.
Kelp forests, globally distributed in cool temperate and polar waters, are renowned for their pivotal role in supporting species diversity and fostering macroalgae productivity. These high-canopy algal ecosystems dynamically influence their surroundings, particularly by altering the physicochemical properties of seawater. This review article aims to underscore the significance of kelp forests in modifying water masses. By serving as effective carbon sinks through the absorption of bicarbonate (HCO 3 −) and carbon dioxide (CO 2) for photosyn-thesis, kelp forests mitigate nearby acidity levels while enhancing dissolved oxygen concentrations, essential for sustaining diverse marine communities. Additionally, kelp beds have exhibited the need to use inorganic ions (NO 3 − , NO 2 − , PO 4 3−) from seawater in order to grow, albeit with associated increases in NH 4 + concentrations. Specific examples and findings from relevant studies will be presented to illustrate the profound impact of kelp forests on seawater chemistry, emphasizing their vital role in marine ecosystems.
Climate change is affecting marine ecosystems in many ways, including raising temperatures and leading to ocean acidification. From 2014 to 2016, an extensive marine heat wave extended along the west coast of North America and had devastating effects on numerous species, including bull kelp (Nereocystis luetkeana). Bull kelp is an important foundation species in coastal ecosystems and can be affected by marine heat waves and ocean acidification; however, the impacts have not been investigated on sensitive early life stages. To determine the effects of changing temperatures and carbonate levels on Northern California's bull kelp populations, we collected sporophylls from mature bull kelp individuals in Point Arena, CA. At the Bodega Marine Laboratory, we released spores from field-collected bull kelp, and cultured microscopic gametophytes in a common garden experiment with a fully factorial design crossing modern conditions (11.63 ± 0.54°C and pH 7.93 ± 0.26) with observed extreme climate conditions (15.56 ± 0.83°C and 7.64 ± 0.32 pH). Our results indicated that both increased temperature and decreased pH influenced growth and egg production of bull kelp microscopic stages. Increased temperature resulted in decreased gametophyte survival and offspring production. In contrast, decreased pH had less of an effect but resulted in increased gametophyte survival and offspring production. Additionally, increased temperature significantly impacted reproductive timing by causing female gametophytes to produce offspring earlier than under ambient temperature conditions. Our findings can inform better predictions of the impacts of climate change on coastal ecosystems and provide key insights into environmental dynamics regulating the bull kelp lifecycle.
The conservation, restoration, and improved management of terrestrial forests significantly contributes to mitigate climate change and its impacts, as well as providing numerous co-benefits. The pressing need to reduce emissions and increase carbon removal from the atmosphere is now also leading to the development of natural climate solutions in the ocean. Interest in the carbon sequestration potential of underwater macroalgal forests is growing rapidly among policy, conservation, and corporate sectors. Yet, our understanding of whether carbon sequestration from macroalgal forests can lead to tangible climate change mitigation remains severely limited, hampering their inclusion in international policy or carbon finance frameworks. Here, we examine the results of over 180 publications to synthesise evidence regarding macroalgal forest carbon sequestration potential. We show that research efforts on macroalgae carbon sequestration are heavily skewed towards particulate organic carbon (POC) pathways (77% of data publications), and that carbon fixation is the most studied flux (55%). Fluxes leading directly to carbon sequestration (e.g. carbon export or burial in marine sediments) remain poorly resolved, likely hindering regional or country-level assessments of carbon sequestration potential, which are only available from 17 of the 150 countries where macroalgal forests occur. To solve this issue, we present a framework to categorize coastlines according to their carbon sequestration potential. Finally, we review the multiple avenues through which this sequestration can translate into climate change mitigation capacity, which largely depends on whether management interventions can increase carbon removal above a natural baseline or avoid further carbon emissions. We find that conservation, restoration and afforestation interventions on macroalgal forests can potentially lead to carbon removal in the order of 10's of Tg C globally. Although this is lower than current estimates of natural sequestration value of all macroalgal habitats (61-268 Tg C year-1 ), it suggests that macroalgal forests could add to the total mitigation potential of coastal blue carbon ecosystems, and offer valuable mitigation opportunities in polar and temperate areas where blue carbon mitigation is currently low. Operationalizing that potential will necessitate the development of models that reliably estimate the proportion of production sequestered, improvements in macroalgae carbon fingerprinting techniques, and a rethinking of carbon accounting methodologies. The ocean provides major opportunities to mitigate and adapt to climate change, and the largest coastal vegetated habitat on Earth should not be ignored simply because it does not fit into existing frameworks.
Ecology Letters (2010) 13: 685–694
Successful mitigation of negative effects of global warming will depend on understanding the link between physiological and ecological responses of key species. We show that while metabolic adjustment may assist Australasian kelp beds to persist and maintain abundance in warmer waters, it also reduces the physiological responsiveness of kelps to perturbation, and suppresses canopy recovery from disturbances by reducing the ecological performance of kelp recruits. This provides a warning not to rely solely on inventories of distribution and abundance to evaluate ecosystem function. The erosion of resilience is mediated by a shift in adult-juvenile interactions from competitive under cool to facilitative under warm conditions, supporting the prediction that positive interactions may become increasingly important in a warmer future. Kelp beds may remain intact but with a lower threshold for where additional impacts (e.g., extreme storms or reduced water quality) will lead to persistent loss of habitat and ecological function.
Significance
Kelp forests support diverse and productive ecological communities throughout temperate and arctic regions worldwide, providing numerous ecosystem services to humans. Literature suggests that kelp forests are increasingly threatened by a variety of human impacts, including climate change, overfishing, and direct harvest. We provide the first globally comprehensive analysis of kelp forest change over the past 50 y, identifying a high degree of variation in the magnitude and direction of change across the geographic range of kelps. These results suggest region-specific responses to global change, with local drivers playing an important role in driving patterns of kelp abundance. Increased monitoring aimed at understanding regional kelp forest dynamics is likely to prove most effective for the adaptive management of these important ecosystems.
No turning back?
Ecosystems over time have endured much disturbance, yet they tend to remain intact, a characteristic we call resilience. Though many systems have been lost and destroyed, for systems that remain physically intact, there is debate as to whether changing temperatures will result in shifts or collapses. Wernburg et al. show that extreme warming of a temperate kelp forest off Australia resulted not only in its collapse, but also in a shift in community composition that brought about an increase in herbivorous tropical fishes that prevent the reestablishment of kelp. Thus, many systems may not be resilient to the rapid climate change that we face.
Science , this issue p. 169
Biological invasions continue to increase around the world, with impacts on many coastal marine systems. Here we review the South African marine invasion literature which, despite the field being relatively new, has grown to have significant presence in both the local and international arenas. Of the 79 papers reviewed, 70% focused on the establishment and spread of alien species, with modes of transport and introduction largely overlooked. An emphasis was also apparent towards field studies, in particular survey work, with few experimental studies. The overwhelming majority of papers focused on a single species, the Mediterranean mussel Mytilus galloprovincialis, reflecting the scale of this invasion and the tractable nature of rocky shores as study systems. With the exception of this one species, the impacts of marine alien species have rarely been quantified. We suggest that future research extends the taxonomic coverage of present work and develops a better understanding of the mechanisms of introduction, establishment and spread of marine alien species. Through an experimental approach, the drivers of altered ecological patterns and processes resulting from invasions should be addressed, providing insight into associated impacts. This approach will maintain the local applicability and international relevance of South African marine invasion research.
An increasing amount of information is being collected on the ecological and socio-economic value of goods and services provided by natural and semi-natural ecosystems. However, much of this information appears scattered throughout a disciplinary academic literature, unpublished government agency reports, and across the World Wide Web. In addition, data on ecosystem goods and services often appears at incompatible scales of analysis and is classified differently by different authors. In order to make comparative ecological economic analysis possible, a standardized framework for the comprehensive assessment of ecosystem functions, goods and services is needed. In response to this challenge, this paper presents a conceptual framework and typology for describing, classifying and valuing ecosystem functions, goods and services in a clear and consistent manner. In the following analysis, a classification is given for the fullest possible range of 23 ecosystem functions that provide a much larger number of goods and services. In the second part of the paper, a checklist and matrix is provided, linking these ecosystem functions to the main ecological, socio–cultural and economic valuation methods.
Studies of temperate rocky reef communities have added much to our understanding of ecology. However, data on these reef communities can be difficult to obtain; wind, waves, and poor underwater visibility often prevent research diving, and even under the best conditions only a few hours a day can be spent underwater collecting data. Here, we present data on temperate subtidal reef communities at 33 sites, almost half of which the National Park Service has sampled annually since 1982. We present core data sets describing the population dynamics of 16 fish, 37 invertebrate, and 15 algal taxa. We include supplementary data sets documenting the size structure of key species, the relative abundance of all fish, the recruitment of selected invertebrates, and the subtidal water temperature at each site through time. Taken together, these data provide one of the most comprehensive descriptions of nearshore reef community dynamics ever assembled.
The chapter summarizes the ecology of the subtidal reefs of South Africa. Discussions include the role of wind, productivity, and oceanographic conditions, the important role of currents and the physical forces as well as the species interactions, including rock lobsters, abalone, and sea urchins.
Recent declines and losses of highly productive and diverse kelp beds have been observed worldwide and linked to increases in ocean temperature. We investigated the impacts of 4 temperature treatments (11, 14, 18 and 21°C) on growth, net length change and mortality of the dominant kelp species in Nova Scotia: Saccharina latissima, Laminaria digitata and Agarum clathratum. Growth rates of A. clathratum were reduced at 18°C over 3 wk of exposure, and all species experienced negative net changes in length at this temperature. Exposure to 21°C led to tissue loss at least twice that observed at 11°C and mortality within the first 2 wk of exposure. Exposure to 21°C for 1 wk reduced blade tissue strength (breaking stress) and extensibility (breaking strain) by 40 to 70% in S. latissima and L. digitata, and all 3 species exhibited reduced strength after 3 wk exposure to 18°C. Histological examination of the blade tissue showed temperature-induced damage to the cellular structure of blades of S. latissima and L. digitata. A. clathratum displayed limited tissue damage and was less susceptible to temperature-induced tissue weakening and loss. Our findings provide a mechanism by which rising temperatures could contribute to observed population declines of kelp species.
Predicting the effect of climate change on communities requires an understanding of the effects of environmental conditions on species and their interactions. We investigated the potential for warming seawater temperature to modify the interactions of the gastropod mesograzer Lacuna vincta and the invasive bryozoan Membranipora membranacea with kelps in Nova Scotia. The nutritional content (C/N) of the kelps Saccharina latissima, Laminaria digitata and Agarum clathratum were unaffected by temperature (11, 18 and 21°C), and chemical defenses (phlorotannins) were reduced only in A. clathratum after 1 wk exposure to 21°C. C/N and phlorotannin content increased over the season in S. latissima collected monthly in summer 2013 and 2014. The effect of temperature-induced changes in kelp on the grazing of L. vincta was assessed using feeding experiments with S. latissima pretreated at 11 or 21°C. Snails consumed more kelp pretreated at 21°C only when grazing rate was high. The quality of S. latissima as a food source for L. vincta was not affected by temperature, as diets of kelp pretreated at 11 and 21°C supported similar growth, reproduction, and survival of snails. Temperature also did not affect the quality of kelp as a substrate for M. membranacea, since settlement rates were not different between S. latissima pretreated at ambient temperature (9 to 14) and 21°C. The absence of temperatureinduced changes in kelp quality suggests that the effects of L. vincta and M. membranacea will act additively with the direct effects of temperature and cause increased biomass loss from kelp beds.
The NansClim project (2010-2013) represented a regional collaboration to assess the effects of climate on Benguela dynamics. Based on in situ (since the 1960s in Namibia and South Africa and 1985 in Angola) and satellite (since the 1980s) observations, the project focussed on four subsystems, namely the Angola subtropical, northern Benguela upwelling, southern Benguela upwelling and Agulhas Bank. This contribution summarizes the findings for selected key questions, ranging from changes in the physico-chemical habitats, plankton, pelagic and demersal fish communities, to cross-cutting evaluation at subsystem and regional scales. The results underline the overriding importance to of considering the combined effects of climate and fishing as drivers of the dynamics of the ecosystem components. Each subsystem currently continues to function largely as a separate entity as described in earlier reviews. However, some changes have been observed across several subsystems, e.g., a coherent shift from one relatively stable period to another occurred in the northern and southern Benguela in the mid-1990s. Future climate change could weaken the boundaries between the four subystems. The findings underline the need for continued regional research collaboration and regional surveys focussed at ecosystem, rather than resource, assessment. Our conclusions include implications for ecosystem-based fisheries management, and recommendations for future regional research.
Overfishing and human-induced climate change are putting severe pressure on marine ecosystems. In the southern Benguela, most of South Africa's commercial fisheries have a long history of exploitation and this, coupled with spatio-temporal changes in key species over the last three decades has severely impacted some of South Africa's fisheries and ecosystems. This review summarizes these spatio-temporal changes and investigates possible drivers thereof. It incorporates both past and current research, with a large portion of the latter having formed part of the University of Cape Town's Ma-Re BASICS (Marine Research in the Benguela and Agulhas Systems for supporting Interdisciplinary Climate-change Science) 2010–2013 program. Almost all described changes involve a temporal decline or a spatial shift in species. Fishing seems to have played a role in many of the observed stock declines, for example through geographically disproportionate catches in relation to stock distribution. In some cases, changes in the physical environment seem to have played an additional role, e.g., rock lobsters on the west coast have been affected by fishing as well as changes in the physical environment. In almost all cases these changes have taken place since the 1980s/1990s, except for one or two resources, which have experienced declines since at least the mid 20th century. Spatial shifts in species have either involved an eastward expansion of cool-water species, including kelps, rock lobster and pelagic fish, or a retraction of warm-water species such as the brown mussel, suggesting a cooling of inshore waters along the south-west coast since the 1980s. This suggested cooling is revealed in ocean temperature (SST Pathfinder), wind and upwelling data for the Cape Peninsula and south-west coast region during the same period. The absence or inconsistency of long-term data is problematic when trying to identify drivers of ecosystem change, and actual ecosystem change itself. We discuss this using ocean temperature in the southern Benguela as an example. In addition, the complex interplay between climate and anthropogenic (notably fishing) drivers makes identification of drivers difficult and disentangling these combined effects will require interdisciplinary collaboration, co-ordinated ecosystem projects, increased modelling effort and the continuation, but also establishment, of new, long-term monitoring studies.
Repeat photography was used to illustrate long-term changes occurring in coastal habitats in the Western Cape, South Africa. Historic images were sourced from books and theses, the public and subject specialists, and repeat photographs were then taken from the same perspectives. Visible changes could be categorised into four types: (1) changes in species’ ranges; (2) biological invasions; (3) sea level changes; and (4) direct engineering impacts. In terms of range changes, the images depict a progressive easterly spread of the cold-water kelp Ecklonia maxima and parallel easterly contraction of the warmer-water mussel Perna perna, both evidence for declining water temperatures along the South-West Coast. Since c. 1980 most shores have also become conspicuously invaded by the alien Mediterranean mussel Mytilus galloprovincialis, while those on the West Coast have also been visibly invaded by the more-recently introduced Pacific barnacle Balanus glandula. No changes in vertical zonation due to changing sea levels could be detected, despite suitable images being available. Construction along the shore has radically altered the appearance of the shoreline in urban areas. Repeat photography thus proved a useful tool for both detecting and dramatically illustrating historic changes over the past century. These changes have altered substantially both the appearance and ecological attributes of many rocky shores in this region.
An eastward shift in the center of abundance of the South African rock lobster Jasus lalandii occurred during
the early 1990s into an area known as East of Cape Hangklip (EOCH). Given (1) the predatory capabilities of J.
lalandii, (2) an intricate relationship between the urchin Parechinus angulosus and juveniles of the abalone
Haliotis midae, and (3) existing over-exploitation of elements of the ecosystem, the ‘lobster invasion’ has
major implications for the benthic ecosystem and associated fisheries. We surveyed the abundance of J.
lalandii and the benthic community composition EOCH at six sites (three ‘invaded’ and three ‘non-invaded’
by J. lalandii), in three different depth zones (b5 m, 6–12 m and 13–20 m). At all depths, J. lalandii was
significantly more abundant in invaded areas than in non-invaded areas, and benthic communities were
significantly different. The high densities of rock lobsters at invaded sites led to cascading effects including
elimination of urchins and depletion of grazers, consequent enhancement of macroalgae, and diminishment
of encrusting corallines. Non-invaded sites had few lobsters, abundant herbivores, less macroalgae and more
encrusting corallines. Elimination of urchins in the invaded area has important implications, as juveniles of
the commercially harvested abalone H. midae depend on shelter beneath urchins in this region. Floral species
diversity was greater at invaded sites and increased with depth, whereas faunal species diversity was greater
at non-invaded sites but also increased with depth. The depths at which strongest effects of J. lalandii were
felt coincided with the depth of maximum abundance of the urchin P. angulosus, the abalone H. midae, the
kelp Ecklonia maxima and encrusting corallines, with serious consequences for associated fisheries and the
benthic community. We argue that the differences between invaded and non-invaded areas are sufficient to
recognize that they are alternate stable-states and constitute a regime shift.
Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to 'barrens' when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs.
Since commercial use of southern African seaweeds began in the early 1950s, six genera (Ecklonia, Laminaria, Gracilaria, Gelidium, Gigartina and Porphyra) have been collected or harvested, and most of this material has been exported for use in various colloid industries. Several other genera show potential for either harvesting (e.g. Hypnea) or mariculture (e.g. Suhria). Currently, the southern African industry earns more than 2,3 million US $ per annum and provides employment for approximately 2 000 people (half of them part-time), mostly in economically depressed rural areas. In this article, available data on commercial and research aspects of the seaweed industry and the regulations governing exploitation of natural populations on the coasts of southern Africa (South Africa, Transkei, Ciskei and Namibia) are considered. Where there is a lack of biological information necessary for further development of the local industry, future research directions are suggested.
The fauna and flora of two sublittoral communities situated in close proximity on the west coast of South Africa are described and shown to be radically different, despite the fact that both experience similar physical conditions. One of these communities, at Marcus Island, has prolific beds of the black mussel Choromytilus meridionalis (35 954 g wet weight·m−2) accompanied by a large number of other species, notably sea urchins, holothurians, brittle stars, whelks and barnacles. In contrast, the other site, Malgas Island, is dominated by a large population of rock lobsters Jasus lalandii together with a dense seaweed flora (3 866 and 4 402 g wet weight·m−2 respectively). The numbers of species are similar at both sites (102 at Malgas Island and 107 at Marcus Island) but only 34 per cent are common to both localities. Although preliminary research indicates that the two sites have fairly similar physical conditions and bottom topography, they maintained their contrasting communities for the whole research period (1983–1986) and have probably done so for at least nine years, suggesting that they represent two stable alternative states of the same ecosystem. In the absence of rock lobsters at Marcus Island, wave action and inter/intraspecific competition are the main forces structuring the benthic community. Stability is maintained here by the resilience and rapid recovery of the mussel population after disturbance by storms. Where rock lobsters are abundant, as at Malgas Island, intense predation pressure is the main force controlling the structure of the benthos, and it is continually maintained because the rock lobsters are resistant to the effect of storms. Therefore, the presence or absence of high densities of rock lobsters is fundamental to the maintenance of these two contrasting communities.
The exchange of energy and nutrients between ecosystems (i.e., resource subsidies) plays a central role in ecological dynamics over a range of spatial and temporal scales. Little attention has been paid to the role of anthropogenic impacts on natural systems in altering the magnitude, timing, and quality of resource subsidies. Kelp ecosystems are highly productive on a local scale and export over 80% of kelp primary production as detritus, subsidizing consumers across broad spatial scales. Here, we generate a model of detrital production from a kelp bed in Nova Scotia to hindcast trends in detrital production based on temperature and wave height recorded in the study region from 1976 to 2009, and to project changes in detrital production that may result from future climate change. Historical and projected increases in temperature and wave height led to higher rates of detrital production through increased blade breakage and kelp dislodgment from the substratum, but this reduced kelp biomass and led to a decline in detrital production in the long-term. We also used the model to demonstrate that the phase shift from a highly productive kelp bed to a low-productivity barrens, driven by the grazing activity of sea urchins, reduces kelp detrital production by several orders of magnitude, an effect that would be exacerbated by projected increases in temperature and wave action. These results indicate that climate-mediated changes in ecological dynamics operating on local scales may alter the magnitude of resource subsidies to adjacent ecosystems, affecting ecological dynamics on regional scales.
Seagrasses support a great diversity of epiphytic organisms. There are no detailed published accounts of algae and animals growing on seagrasses in South Africa. The seagrass Thalassodendron leptocaule (previously known as Thalassodendron ciliatum) is unique among southern African seagrasses in that it occurs on exposed rocky outcrops along the Mozambican and north-eastern South African coasts; most other seagrasses are restricted to sheltered bays and estuaries. Here we present accounts of species of flora and fauna identified growing epiphytically on this seagrass in northern KwaZulu-Natal. A total of 52 taxa of macroalgae and 204 species of macroinvertebrates were identified as epiphytic on South African T. leptocaule. The most frequently observed macroalgal epiphytes were predominantly Rhodophyta and were common among periodically exposed, intertidal and subtidal habitats. The crustose red coralline algae Pneophyllum amplexifrons and Hydrolithon farinosum were frequently observed, primarily on stems and leaves of the seagrass respectively. The most diverse groups of epiphytic invertebrates were Arthropoda, Annelida and Mollusca, which together comprised 76% of the macroinvertebrate species recorded. This seagrass species is evidently an important substratum and ecosystem that supports a hidden wealth of biodiversity.
Kelp forests along temperate and polar coastlines represent some of most diverse and productive habitats on the Earth. Here, we synthesize information from >60 years of research on the structure and functioning of kelp forest habitats in European waters, with particular emphasis on the coasts of UK and Ireland, which represents an important biogeographic transition zone that is subjected to multiple threats and stressors. We collated existing data on kelp distribution and abundance and reanalyzed these data to describe the structure of kelp forests along a spatial gradient spanning more than 10° of latitude. We then examined ecological goods and services provided by kelp forests, including elevated secondary production, nutrient cycling, energy capture and flow, coastal defense, direct applications, and biodiversity repositories, before discussing current and future threats posed to kelp forests and identifying key knowledge gaps. Recent evidence unequivocally demonstrates that the structure of kelp forests in the NE Atlantic is changing in response to climate- and non-climate-related stressors, which will have major implications for the structure and functioning of coastal ecosystems. However, kelp-dominated habitats along much of the NE Atlantic coastline have been chronically understudied over recent decades in comparison with other regions such as Australasia and North America. The paucity of field-based research currently impedes our ability to conserve and manage these important ecosystems. Targeted observational and experimental research conducted over large spatial and temporal scales is urgently needed to address these knowledge gaps.
Kelp beds, besides being one of the most important benthic resources in northern Chile, provide a variety of environmental goods and services. In order to evaluate economically the wild kelp populations in northern Chile (26° to 32° S) more than simply their commercial value as a source of raw materials for alginate extraction, we used several economic indicators to holistically assess the value of a group of brown seaweeds of economic importance, Lessonia spp. and Macrocystis pyrifera: (1) market value of biomass as a source of raw material for extraction of alginic acid, (2) market value of associated species of economic importance, (3) value as a source of scientific information, (4) value as a climate buffer (CO2 capture and release of O2), (5) value of associated biodiversity (non-commercial species), (6) value as cultural heritage and (7) value as a reservoir of biodiversity. Existence values of kelp beds which estimate the willingness of citizens to pay and work without payment to preserve the ecosystem were calculated using the contingent valuation technique. The results indicate that kelp beds in northern Chile have a total value of US $540 million. Of this total, kelp fishery accounts for 75 % and associated-species fisheries account for 15 %. In this context, the economic value of Chilean kelp beds is mainly associated with the industry of alginate extraction. By contrast, existence value as a source of scientific information or environmental buffer for CO2 capture or O2 production represents only 9 % of the total value, representing a very low relative importance to society. The economic valuation of coastal resources and marine ecosystems is a complementary tool for decision making and implementation of public policies related to the conservation and sustainable exploitation of renewable resources and their ecosystems.
Potential fishery benefits of Marine Protected Areas (MPAs) are widely acknowledged, yet seldom demonstrated, as fishery data series that straddle MPA establishment are seldom available. Here we postulate, based on a 15-year time series of nation-wide, spatially referenced catch and effort data, that the establishment of the Goukamma MPA (18 km alongshore; 40 km(2)) benefited the adjacent fishery for roman (Chrysoblephus laticeps), a South African endemic seabream. Roman-directed catch-per-unit-effort (CPUE) in the vicinity of the new MPA immediately increased, contradicting trends across this species' distribution. The increase continued after 5 years, the time lag expected for larval export, effectively doubling the pre-MPA CPUE after 10 years. We find no indication that establishing the MPA caused a systematic drop in total catch or increased travel distances for the fleet. Our results provide rare empirical evidence of rapidly increasing catch rates after MPA implementation without measurable disadvantages for fishers.
Kelp forests, highly diverse cold water communities organized around the primary productivity and physical structure provided by members of the Laminariales, support a variety of fisheries, and the kelp itself is harvested for alginates. Worldwide, these communities generally share susceptibility to destructive overgrazing by sea urchins. The impact of sea-urchin grazing is governed by the ratio between food availability and grazing pressure, thus factors affecting the abundance of both urchins and kelps are central to ecosystem integrity. Some kelp ecosystems share a second generality, the association of exploitation of various urchin predators with destructive levels of urchin grazing, leading to cascading implications for other species dependent on the productivity and habitat provided by the kelps. Competition between abalones and sea urchins also affects some kelp communities. These ecosystem-structuring processes are complicated by a variety of bottom-up and top-down factors, including variability in ocean climate affecting kelp productivity and recruitment of key species, and echinoid disease, potential ecosystem effects of fisheries for predators, abalones, sea urchins, and kelps are reviewed biogeographically. Given the hundreds to thousands of years that many nearshore marine ecosystems have been exploited, no-take marine reserves may be the only way to determine the true ecosystem effects of fishing. (C) 2000 International Council for the Exploration of the Sea.
