Article

Substratum heterogeneity of dredged vs un-dredged maerl grounds

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Abstract

Maerl grounds are comparable to sea grass beds in terms of their high biodiversity, and are characterized by abundant juveniles of species such as the queen scallop, Aequipectenopercularis. Maerl grounds impacted by towed demersal fishing gears are structurally less heterogeneous than pristine, un-impacted maerl grounds, diminishing the biodiversity potential of these habitats.

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... También soporta una explotación indirecta por pesca de arrastre, así como otras actividades como los amarres con cadenas y fondeos no regulados (Hall-Spencer & Moore 2000, Bordehore et al. 2003). La eutrofización, la contaminación por metales pesados, la acuicultura y la introducción de especies alóctonas también han sido reconocidas como efectos negativos sobre esta comunidad (Hily et al.1992, Grall & Glémarec 1997, De Grave & Whitaker 1999, De Grave et al. 2000, Barberá et al. 2003, Kamenos et al. 2003, Wilson et al. 2004. ...
... Con el total de las muestras se ha generado una base de datos en la que se ha incluido la información ambiental y geográfica de cada inventario (localidad y UTM, tipo sustrato, extensión de la población, profundidad, fecha, método de recolección, salinidad, temperatura, presencia/ausencia de 'ripples') y de la estructura y flora de la comunidad (cobertura de maërl, proporción de maërl vivo/maërl muerto, espesor de la capa viva de maërl, especies asociadas, estado reproductor, etc.). La información biológica de la comunidad fue empleada para valorar el estado de conservación de los bancos de maërl de forma similar al realizado por Foster et al. (1997), BIOMAERL Team (1999), Kamenos et al. (2003) ...
... Diversidad biológica de la comunidad de maërl en Galicia Estudios previos indican una diversidad faunística importante asociada a la comunidad de maërl en Galicia (Cadée 1968, Mora 1980, BIOMAERL Team 1999, Barberá et al. 2003. La estructura tridimensional del maërl favorece la existencia de un amplio rango de nichos ecológicos propicios para el desarrollo de algunas especies de interés comercial, especialmente moluscos bivalvos (Grall & Glemarec 1997, Birkett et al. 1998, BIOMAERL Team 1999, Hall-Spencer & Moore 2000, Grall 2003, Barberá et al. 2003, Kamenos et al., 2003. La riqueza florística de los bancos de maërl gallegos asciende a 232 especies: 9 Cyanophyta, 160 Rhodophyta, 36 Heterokontophyta y 27 Chlorophyta (Peña & Bárbara 2007a), lo cual representa aproximadamente el 40% de la flora marina registrada en la costa de Galicia (Bárbara et al. 2005). ...
... Dire d'experts Publications examinées en comité de lecture : Barbera et al., 2003 ;Bosence & Wilson, 2003 ;Hall-Spencer et al., 2003, Hauton et al., 2003Kamenos et al., 2003 ;Wilson et al., 2004 Tassement H F TH F TF F Les bancs de maërl sur sables grossiers et graviers sont très résistants à la compression verticale en raison de leur structure calcifiée. Les thalles de la strate superficielle peuvent être cassés, sans que cela affecte l'habitat en général. ...
... Les thalles de la strate superficielle peuvent être cassés, sans que cela affecte l'habitat en général. Publications examinées en comité de lecture : Barbera et al., 2003 ;Bosence & Wilson, 2003 ;Hall-Spencer et al., 2003, Hauton et al., 2003Kamenos et al., 2003 ;Wilson et al., 2004 Abrasion Une augmentation trop importante de l'hydrodynamisme induit une érosion des thalles superficiels, et une réduction de l'hydrodynamisme induit un envasement délétère. La résistance est qualifiée de faible et la résilience de nulle en raison du temps nécessaire à la reconstruction d'une communauté fonctionnelle. ...
... Le temps nécessaire à la recolonisation par les espèces caractéristiques de l'habitat (espèces à cycles courts), est estimé à environ 2-5 ans. Publications examinées en comité de lecture : Barbera et al., 2003 ;Bosence & Wilson, 2003 ;Hall-Spencer et al., 2003, Hauton et al., 2003Kamenos et al., 2003 Publications examinées en comité de lecture : Barbera et al., 2003 ;Bosence & Wilson, 2003 ;Hall-Spencer et al., 2003, Hauton et al., 2003Kamenos et al., 2003 Abrasion profonde Une augmentation trop importante de l'hydrodynamisme induit une érosion des thalles superficiels, et une réduction de l'hydrodynamisme induit un envasement qui peut être délétère s'il persiste. La résistance est qualifiée de modérée pour une pression de courte durée et la résilience de nulle en raison du temps nécessaire à la reconstruction d'une communauté fonctionnelle. ...
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Les évaluations de sensibilité ont été réalisées selon la méthodologie décrite précédemment (La Rivière et al., 2015) par un groupe d’experts spécialistes des habitats benthiques, co-auteurs de ce rapport, lors de deux ateliers travail qui se sont déroulés à Brest à l’automne 2016. Elles se basent sur les meilleures connaissances disponibles à ce jour et ont été complétées par l’avis de ces experts. Il a été choisi de réaliser les évaluations de sensibilité à travers des ateliers de travail thématiques afin de (i) minimiser le biais d’interprétation de chaque expert en clarifiant le contexte d’application des évaluations, (ii) mutualiser les connaissances (en particulier sur des habitats peu connus), et ainsi (iii) maximiser la robustesse des évaluations. Les évaluations ont été réparties en deux ateliers de travail (un atelier par type de substrat – habitats de substrats durs ou de substrats meubles) animés par le SPN et réunissant des experts benthologues. Des experts externes, cités comme contributeurs au projet, ont été sollicités lorsqu’une expertise spécifique complémentaire s’est révélée nécessaire. Ce travail permettra de constituer une base de données, générique et partagée, de sensibilité des habitats benthiques. Une matrice synthétique illustrant les liens potentiels entre les activités anthropiques et les pressions utilisées pour les analyses de sensibilité, compilée à partir des informations déjà disponibles et validées (rapports de l’évaluation initiale de la DCSMM, référentiels pour la gestion dans les sites Natura 2000, etc.) a été élaborée en collaboration avec des experts techniques (BRGM, IFREMER) et est disponible sur la page du programme sur le site de l’INPN. Cette matrice activités/pressions, mise en commun avec les matrices de sensibilité habitats/pressions, permettra d’identifier les enjeux potentiels de sensibilité habitats/activités. Ce rapport présente la première version des évaluations de sensibilité des habitats élémentaires d’Atlantique, de Manche et de Mer du Nord à certaines pressions physiques. Ces habitats élémentaires constituent la déclinaison française des habitats génériques de l’Annexe I de la DHFF, et sont décrits dans le Cahier d’habitats côtiers (Bensettiti et al., 2004). Les évaluations de sensibilité des habitats définis dans la typologie des habitats marins benthiques de la Manche, de la Mer du Nord et de l’Atlantique (une fois mise à jour) à toutes les pressions (pressions physiques, biologiques et chimiques) seront réalisées dans un deuxième temps.
... While live maerl can cope with extreme ranges of temperature, salinity or metal pollution (Wilson et al., 2004), it is fragile, slowgrowing and can be easily broken and killed by demersal towed fishing gear (Hall-Spencer and Moore, 2000) and smothered by sediment (Wilson et al., 2004). Live maerl has greater heterogeneity than dead maerl (Kamenos et al., 2003). For example, the matrix of spaces between the maerl thalli provide refuge from predation for post-settled juvenile queen scallops (Kamenos et al., 2004 a). ...
... Increasing amounts of live maerl fragments on dead maerl beds correlated with an increasing number of epibenthic taxa in Falmouth suggesting that the presence of live maerl on dead maerl beds can affect aspects of biodiversity in marine systems. This could be due to the greater heterogeneity of live maerl thalli compared to dead maerl (Kamenos et al., 2003). However, there was no significant correlation observed in Jersey or between percentage % Occurrence of live maerl and Abundance of epifauna. ...
... In Falmouth, maerl beds containing live maerl thalli had a greater Number of taxa and a greater Abundance of epifauna. This is most likely due to the greater heterogeneity of live maerl than other substrata (Kamenos et al., 2003), but it is not clear why similar trends were not observed for Jersey. However, maerl beds sampled in Jersey were at greater depths than Falmouth and were sampled in a different season. ...
... Maerl grounds, which vary in size from tens to thousands of square metres, consist of loose-lying, coralline red algae (Giraud and Cabioch, 1976), and are in areas characterized by extensive water movement (tidal and/or wave action) in the photic zone (Woelkerling, 1988). Live maerl grounds are highly biodiverse (BIOMAERL team, 2003;Steller et al., 2003), and have significantly greater heterogeneity than common adjacent substrata, including gravel, sand, and impacted dead maerl (Kamenos et al., 2003). A single physical impact event may significantly reduce the heterogeneity of maerl thalli to that of a gravel substratum, by breakage, and may lead to subsequent death of the maerl (Hall-Spencer and Moore, 2000b;Kamenos et al., 2003). ...
... Live maerl grounds are highly biodiverse (BIOMAERL team, 2003;Steller et al., 2003), and have significantly greater heterogeneity than common adjacent substrata, including gravel, sand, and impacted dead maerl (Kamenos et al., 2003). A single physical impact event may significantly reduce the heterogeneity of maerl thalli to that of a gravel substratum, by breakage, and may lead to subsequent death of the maerl (Hall-Spencer and Moore, 2000b;Kamenos et al., 2003). To date, no data are available on the effects of maerl on juvenile gadoid distributions, a topic addressed herein. ...
... Maerl grounds are slow-growing and easily damaged (Hall-Spencer and Moore, 2000a;BIOMAERL team, 2003;Kamenos et al., 2003) and are protected under the EC Habitats Directive, so mobile gears were not used for sampling purposes. Static gear trials have shown that fykenets are successful at catching juvenile gadoids (Nostvik and Pedersen, 1999). ...
Article
The indirect effects of demersal fisheries, such as habitat degradation, are currently thought to be impacting gadoid stocks. Maerl fulfils nursery area prerequisites for several invertebrate species, so its role in similar ecosystem service provision for gadoids has been addressed. Juvenile cod (Gadus morhua), saithe (Pollachius virens), and pollack (Pollachius pollachius) in shallow (<7 m) inshore waters were surveyed with fykenets and scuba off western Scotland over a period of 12 months. Juvenile densities were highest from September to November, and at that time, significantly more were present during the day and associated with maerl (that lacked macroalgal cover) than with heavily vegetated rocky and gravel substrata. Juvenile cod were present throughout the year, whereas saithe appeared in July, and pollack from September to January. With its abundance of food, maerl probably has a high holding capacity for juvenile gadoids, and thus is an important part of the inshore nursery system.
... Dredging smothers rhodoliths in silt and mud, and trawling-related impaction crushes the branching matrix, homogenizing the seafloor Hauton 2003;Kamenos 2003). These disturbances can create long-lasting, if not permanent, effects. ...
... The matrix of interstitial spaces provides predation refuge for small invertebrates, a settlement substrate for epiphytes and epifauna, and can act as a nursery habitat (Barbara et al. 2004;Kamenos et al. 2004;Leliaert et al. 2009;Steller and Caceres-Martinez 2009). The complexity, and therefore the inherent benefit of this habitat, is compromised by physical impacts that break branches and fill and reduce the spaces between (Kamenos 2003). ...
Article
Full-text available
Rhodoliths are free-living coralline algae (Rhodophyta) that form large beds on the seafloor. Rhodolith beds are globally widespread and biologically diverse shallow marine habitats. Beds are ecologically sensitive, disturbed by humans, and in Europe are protected by law. While rhodolith beds have been found in California waters at Catalina Island, no literature exists regarding their distribution or ecological significance. This study sought to (1) map the distribution and characterize the rhodolith beds around Catalina, (2) determine the seasonal growth rates, and (3) investigate the effect of common sources of disturbance. A systematic search of shallow subtidal (0-40 meters) areas revealed seven beds. These were mapped by divers using SCUBA. Living and dead rhodolilths and rhodalgal sediments covered approximately 22,900 and 42,696 square meters of seafloor, respectively. Percentage cover, and mean size of living rhodoliths varied across beds. Growth rates varied seasonally but were consistent with global averages; branches grew just over a millimeter a year. Vessel mooring chains were a common source of disturbance, and decreased 3-dimensional rhodolith habitat and living rhodolith cover. More benthic fauna were seen in living beds compared to dead, impacted rhodolith sediments or adjacent sandy benthos. Highly disturbed and slow to recover, this novel habitat should be considered a high priority for future protection, monitoring, and restoration efforts.
... Thus, our findings suggest that overall scallop behaviour is mediated by the interaction between the live maerl (possibly by active molecules such as g-aminobutyric acid and/or physical surface properties ), the heterogeneity of the maerl (the mechanism by which heterogeneity is perceived remains unknown but may be visual or caused by alteration in local flow regimes, Shumway 1991) and the impact of the live maerl and heterogeneity on physiological processes manifesting as cardiac activity. The reduced flow of water associated with substrata with high heterogeneity (Irlandi et al. 1999), such as live maerl in our experiments, does not affect the energy requirements of the juvenile queen scallops, as no differences in HR were observed between scallops on the heterogeneous live maerl and those on dead maerl, sand and no substratum where heterogeneity is significantly lower (Kamenos et al. 2003). However, in the presence of a predator, scallops attached to live maerl had the lowest HR. ...
... Thus observed differences in HR are not merely an artefact of substratum stability and heterogeneity. Our results corroborate the hierarchical preference of juvenile queen scallops for a stable attachment substratum in the absence of a predator and both a stable substratum and high heterogeneity in the presence of a predator (scallops could not choose their attachment substratum, so we could not observe a preference for the live maerl veneer) noted by Kamenos et al. (2003). The observed HR response in these juvenile invertebrates may stimulate a change in behaviour such as locomotory activity or feeding rate. ...
Article
Although the relation between behaviour and stress in humans and other vertebrates is well documented, few comparable observations exist for invertebrates. We addressed this issue by considering the impact of the physical environment on cardiac activity in invertebrates exposed to predation and nonpredation threat scenarios. We used cardiac activity as a proxy of stress in juvenile queen scallops, Aequipecten opercularis, under predation threat by the common starfish, Asterias rubens. Stress levels were monitored in juvenile queen scallops exposed, and not exposed, to predation threat on a substratum known to act as a refuge (live maerl) as well as substrata known not to possess refuge potential (dead maerl, sand and no sediment). In the vicinity of known refuges, stationary scallops under predation threat had significantly lower cardiac activity than individuals in habitats lacking refuges. Scallops not under predation threat did not show significant differences in cardiac activity. These are probably habitat-mediated physiological responses to the presence of a predator and possibly to the availability of suitable attachment substrata. These findings have implications in terms of behavioural physiology in invertebrates.
... Some environmental factors such as water motion, light availability, sedimentation, and depth affect rhodolith size, morphology, stability, and distribution (Steller and Foster 1995, Harris et al. 1996, Basso 1998. The diversity in the rhodolith surrounding sediments appears to be related to the structural complexity provided by the dense aggregations of the rhodoliths and their fragments (Kamenos et al. 2003, Steller et al. 2003, Foster et al. 2007. ...
... Algunos factores ambientales, tales como el movimiento del agua, la disponibilidad de luz, la sedimentación y la profundidad, afectan el tamaño, la morfología, la estabilidad y la distribución de los rodolitos (Steller y Foster 1995, Harris et al. 1996, Basso 1998. La diversidad en los sedimentos circundantes probablemente esté relacionada con la complejidad estructural proporcionada por las densas agregaciones de los rodolitos y sus fragmentos (Kamenos et al. 2003, Steller et al. 2003, Foster et al. 2007). ...
Article
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This study describes the predominantly tropical, subtidal seaweed populations growing on rhodoliths between 4 and 18 m depth in the southern part of Espirito Santo State (Brazil). Qualitative and quantitative sampling revealed species–rich algal communities, comprising 167 species. Three species of rhodophytes represent new records for the Brazilian marine flora (Lithothamnion muelleri, Scinaia aborealis, and Mesophyllum engelhartii). Marked seasonal differences in fleshy algal species composition and abundance were related to seasonal instabilities caused by winter–storm disturbance over the rhodolith beds. In relation to depth, rhodolith density appears to be an important factor for the variation in the abundance of fleshy algae. The rhodolith community is composed of at least seven nongeniculate crustose coralline algal species. Rhodolith beds in southern Espírito Santo State, in an area of 150 km2, provide an important habitat for epibenthic communities, supporting 25% of the known macroalgal species richness along the Brazilian coast.
... Maerl is the collective term for several species of calcified red seaweed, which in their free living form and under favourable conditions can create extensive maerl beds. Maerl beds are often formed in association with sand and gravel and can constitute both live and dead maerl thalli (Kamenos, Moore and Hall-Spencer 2003). Maerl habitats exhibit a high heterogeneity compared to the surrounding substrata (Hall-Spencer and others 2003; Kamenos, Moore and Hall-Spencer 2003). ...
... Maerl beds are often formed in association with sand and gravel and can constitute both live and dead maerl thalli (Kamenos, Moore and Hall-Spencer 2003). Maerl habitats exhibit a high heterogeneity compared to the surrounding substrata (Hall-Spencer and others 2003; Kamenos, Moore and Hall-Spencer 2003). Maerl beds typically develop where there is some tidal flow and are found off the southern and western coasts of the British Isles, but are particularly well developed around the Scottish islands and in sea loch narrows, around Orkney, and in the south in the Fal Estuary. ...
... The highly branched rigid thalli interlock to form a three-dimensional lattice, which provides valuable ecological niches for a diverse range of seaweed and invertebrate species, some of which may be confined to the maerl habitat (Keegan 1974, Bosence 1976, Foster 2001, Steller et al. 2003, McCormack 2006. Recent studies have also highlighted the importance of maerl beds as nursery grounds for commercially harvested gadoid and bivalve species (Kamenos et al. 2003, Uso de técnicas de fechado con carbono radioactivo para interpretar ambientes históricos de bancos de rodolitos Use of radiocarbon dating to interpret past environments of maerl beds C Blake 1 , C Maggs 2 , P Reimer 3 bivalvos de interés comercial (Kamenos et al. 2003(Kamenos et al. , 2004. El valor para la conservación de los bancos de rodolitos ha sido contemplado en la legislación de la Unión Europea y dos especies formadoras de maerl, Phymatolithon calcareum y Lithothamnion corallioides, están incluidas en el Anexo V de la Directiva de la Unión Europea 92/43/EEC (Conservación de los Hábitats Naturales y de la Flora y Fauna Silvestres), como especies de interés para la comunidad cuya recolección silvestre y explotación pueden estar sujetas a medidas de manejo. ...
... The highly branched rigid thalli interlock to form a three-dimensional lattice, which provides valuable ecological niches for a diverse range of seaweed and invertebrate species, some of which may be confined to the maerl habitat (Keegan 1974, Bosence 1976, Foster 2001, Steller et al. 2003, McCormack 2006. Recent studies have also highlighted the importance of maerl beds as nursery grounds for commercially harvested gadoid and bivalve species (Kamenos et al. 2003, Uso de técnicas de fechado con carbono radioactivo para interpretar ambientes históricos de bancos de rodolitos Use of radiocarbon dating to interpret past environments of maerl beds C Blake 1 , C Maggs 2 , P Reimer 3 bivalvos de interés comercial (Kamenos et al. 2003(Kamenos et al. , 2004. El valor para la conservación de los bancos de rodolitos ha sido contemplado en la legislación de la Unión Europea y dos especies formadoras de maerl, Phymatolithon calcareum y Lithothamnion corallioides, están incluidas en el Anexo V de la Directiva de la Unión Europea 92/43/EEC (Conservación de los Hábitats Naturales y de la Flora y Fauna Silvestres), como especies de interés para la comunidad cuya recolección silvestre y explotación pueden estar sujetas a medidas de manejo. ...
Article
Beds of nongeniculate coralline algae, known as rhodolith beds or maerl, occur throughout the world. They are protected under European legislation due to their high conservation value; however, within Europe there are significant areas of dead maerl deposits and the causes of the demise of these past habitats is not always clear. In this study we utilize radiocarbon dating techniques to constrain the time of the maerl bed deaths from a number of historical or pre-historical possibilities. We highlight the threat from burial to these precious habitats, which has implications for contemporary conservation. We found that a maerl bed in Strangford Lough, Northern Ireland, was killed around 4200 14 C BP (before present, AD 1950), which is the same as a previously reported maerl bed death in Marseille, France. This also coincides with evidence of a significant period of climatic change. The case study of Belfast Lough highlights the modern threat to maerl bed by sedimentation caused by channel dredging, which complements previous experimental work.
... Generally, dead maerl has been considered to be of a lower diversity and structural value than live maerl (e.g. Nunn 1992, Kamenos et al. 2003; however, meiofaunal bivalves have been found in greater abundances in the dead maerl matrix than live (Jackson et al. 2004), and a recent comparison of maerl epifauna has shown that the relative importance of dead and live maerl can vary with location (Sheehan et al. 2015). ...
... Similarly, the dead maerl structure in the present study was maintained, indicating a capacity to physically survive the process without the maerl fragments breaking down further. This is in contrast to other physical impacts, such as from scallop dredging, where biogenic carbonate structures tend to be crushed and compacted (Hall-Spencer & Moore 2000, Kamenos et al. 2003), suggesting the dredging method used in this study maintained the integrity of the physical habitat aiding invertebrate survival. This maintenance of structural complexity is also a necessity for successful potential resettlement and re cruitment of the fauna (Kamenos et al. 2004b, Howarth et al. 2011, with a more complex maerl matrix, with a subsequently larger interstitial volume, supporting greater numbers of organisms (Steller et al. 2003). ...
Article
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An experimental trial to mitigate dredging impact was undertaken within Falmouth Harbour, UK, removing a surface layer of dead maerl for storage on a barge and allowing the channel to be deepened before re-laying the maerl. The resilience (resistance and recovery) of the habitat and faunal assemblage to this disturbance was assessed. Six sites each had 2 conditions — a manipulated treatment area where maerl (25 m2 plots, top 0.3 m) was removed, stored on a barge and re-laid by backhoe dredger and a control area — which were cored at 0 (before), 5 and 44 wk after re-lay. PERMANOVA was used to test for differences between condition and time using a 2-factor design. Results should not be extrapolated to live maerl habitats or to large, longlived fauna that may live within them. Following the mechanical disturbance, the maerl matrix structure was altered through loss of fine sediment from the lower half of cores (>10 cm). There was also a significant reduction in the number of taxa and abundance of infauna and a change in the assemblage composition. By Week 44, however, no such significant differences were evident, indicating that the infauna was in a state of recovery. The only response variable showing recovery was annelid biomass. The trial demonstrated that removing and re-laying the top 0.3 m of maerl habitat is technically feasible, and whilst some differences in the habitat structure following re-laying were evident, this did not affect the habitat quality enough to prevent recolonisation of infauna.
... La diversidad de organismos que vive sobre los rodolitos probablemente sea resultado de que proporcionan superficies duras para la fijación en lo que de otra forma sería un fondo suave. La diversidad de la criptofauna de los rodolitos se relaciona con el tamaño del talo, la complejidad y posiblemente la dureza de sus formas ramificadas, mientras que la diversidad en los sedimentos circundantes probablemente esté relacionada con la complejidad estructural de las densas agregaciones de rodolitos y fragmentos de rodolitos (Kamenos et al. 2003, Steller et al. 2003. La diversidad entre las formas rodolíticas más "sólidas", como Lithothamnion muelleri, también puede estar asociada con el tamaño del talo así como con la longevidad. ...
... The diversity of organisms living on rhodoliths most likely results from the provision of hard attachment surfaces on what would otherwise generally be a soft bottom. The diversity of the rhodolith cryptofauna is related to thallus size, complexity and perhaps hardness in branched forms, and the diversity within the surrounding sediments is probably related to the structural complexity provided by dense aggregations of rhodoliths and rhodolith fragments (Kamenos et al. 2003, Steller et al. 2003. The diversity within more "solid" forms like Lithothamnion muelleri may also be related to thallus size but also longevity. ...
Article
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We quantitatively assessed the relative contribution of the rhodolith form of Lithothamnion muelleri, a likely foundation species, to macroorganism diversity in a community also inhabited by the large fucalean Sargassum horridum at a site near Cabo Los Machos at the mouth of Bahía Concepción, Baja California Sur, Mexico. The composition and abundance of seaweeds, epibenthic invertebrates, and fish were estimated in March and October 2003, and invertebrates within rhodoliths (cryptofauna) in March 2003. Rhodoliths and Sargassum horridum had the highest cover of all organisms within the 0.5-km2, 2-8-m-deep cobble-sand site. A total of 29 species of seaweeds, 40 taxa of benthic invertebrates, and 33 species of fish were sampled in transects and quadrats. Macroalgal and fish diversity were similar between sampling times as a result of loss and replacement of taxa, but benthic invertebrate diversity declined without replacement from March to October. Rhodolith cover was similar at both sampling times. The cover and density of S. horridum were highly seasonal, and the non-rhodolith flora changed from abundant S. horridum (35% cover) in March to abundant red algal turf in October (22% cover). The sea urchin Arbacia incisa, tunicates, and polychaetes were the most abundant epibenthic invertebrates in March, but declined by October, the former to zero. Grunts (Haemulon maculicauda) and porgies (Calamus brachysomus) were the most abundant fish at both sampling times, but there were large temporal changes in some other species, especially schooling fishes. Rhodolith density in March was 24 ind m-2, with numerous individuals >8 cm diameter. Fifteen rhodoliths from a range of size classes contained 114 cryptofaunal taxa with an average of 40 taxa /individual in the largest rhodoliths. These results show the importance of rhodolith habitat to diversity, the large temporal changes in some assemblages, and the exceptionally high diversity of this subtropical community.
... Rhodolith habitats are currently at risk from human-induced change, including trawling (Kamenos et al. 2003), turbidity and sedimentation from terrestrial run-off (Harvey and Bird 2008), nutrification from aquaculture (Haskoning UK Ltd 2006), smothering by fine sediment from dredge spoil (Wilson et al. 2004) and storm-water or effluent outfalls (OSPAR 2010). Anthropogenic disturbances can be catastrophic with beds degraded by prawn trawling (Svane et al. 2009), structurally damaged by mobile fishing gear (Bax and Williams 2001), destroyed by scallop dredging and extensively bleached by oil spills (Felder et al. 2014;Fredericq et al. 2014). ...
... The detrimental effects of trawling on rhodolith beds has been established both in Europe Hauton et al. 2003;Kamenos et al. 2003) and Australia. Svane et al. (2009) found that total biomass, abundance and cover in the Spencer Gulf were inversely related to trawl hours, and the lower than expected biodiversity within these rhodolith beds is probably the result of exposure to considerable trawling activity. ...
Article
Rhodolith beds are major marine benthic macrophyte communities, comparable in size and significance to kelp beds, seagrass meadows and coralline reefs. Rhodolith beds are currently 'at risk', both around the world and in Australia, from anthropogenic disturbances such as ocean acidification, coastal degradation and sedimentation. However, knowledge of rhodolith distribution in Australia is limited and beds are currently largely considered to be uncommon and isolated. An extensive review was undertaken using herbarium collections, and relevant scientific and grey literature (journal publications, marine surveys, ships' logs, reference books and websites) for references to rhodoliths and rhodolith beds. Our study has shown that rhodoliths are common throughout 70% of Australia's coastline, ranging from tropical to cold-Temperate waters, down to 117m, forming a vast natural resource in terms of area covered, biodiversity and carbonate production. This review has created a solid foundation for future rhodolith research in Australia by documenting the extent of known rhodolith distribution. It will help inform and influence future research and policy planning on these largely unexplored, highly diverse marine ecosystems.
... They constitute important biogenic carbonate ecosystems (Foster 2001) and refuge for many organisms (Amado-Filho et al. 2007, Foster et al. 2007). In addition, they are also feed for invertebrate species and support species of commercial importance in many coastal areas (Kamenos et al. 2003, Steller et al. 2003. However, physiological knowledge of this algal community is scarce. ...
... Constituyen importantes ecosistemas biogénicos carbonatados (Foster 2001) y son refugio para muchos organismos (Amado-Filho et al. 2007, Foster et al. 2007). Además sirven de alimento para especies de invertebrados y sostienen especies de importancia comercial en muchas áreas costeras (Kamenos et al. 2003, Steller et al. 2003. Sin embargo, el conocimiento fisiológico de esta comunidad de algas es escaso. ...
Article
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Photosynthetic activity was estimated, in 2 different sets of experiments, as in vivo chlorophyll a fluorescence in 2 calcareous red macroalgae: Neogoniolithon brassica-florida, which forms vermetid reefs with Dendropoma petraeum, and the rhodolith-forming Lithophyllum margaritae. In the first set of experiments, vermetid reefs collected from the Cabo de Gata-Níjar Natural Park (Almería, Spain) were incubated for 6 months in outdoor mesocosms at 2 different temperatures: ambient temperature (T) and ambient temperature plus 2 ºC (T+). Daily variations in effective quantum yields were related to the increase in solar radiation. Electron transport rate (ETR) was higher at T+ than at T. Oxygen production, estimated from ETR, was higher in N. brassica-florida growing in vermetid reefs in the coastal area than in those incubated in mesocosms or under laboratory conditions. In the second set of experiments, L. margaritae specimens with or without attached epifauna (mainly sponges) were collected at 2 sites (Pedregoso and CFE) on the Baja California Peninsula, Mexico, and at 2 depths (1 and 2 m). ETR values for rhodoliths collected at 1 m depth and with attached epifauna were higher than those for rhodoliths collected at 2 m depth, indicating the importance of greater incident radiation on photosynthetic activity. Photosynthetic activity was higher in L. margaritae collected from Pedregoso, the site with better water quality (high transparency and low pollution) and rocky substrate availability. In the CFE samples, the photosynthetic efficiency (alphaETR) was highest in rhodoliths with attached epifauna. The highest ETR values for N. brassica-florida at T+ and the highest alphaETR or ETR values for L. margaritae with attached sponges may be explained by the increase in CO2 available for photosynthesis due to the respiration of the associated fauna. The usefulness of in vivo chlorophyll a fluorescence for estimating photosynthetic production in calcareous macroalgae under multifactorial experiments is discussed.
... Rhodolith beds must be thought of as a non-renewable resource (Barbera et al., 2003) due to their extremely low growth rate (1 mm per year) (Blake and Maggs, 2003). For this reason, the two main coralligenous species that characterise it, Phymatolithon calcareum ( Rhodolith bed integrity is threatened by human activities (Kamenos et al., 2003). The loss of habitat heterogeneity and habitat degradation may impact their functioning (Kamenos et al., 2003). ...
... For this reason, the two main coralligenous species that characterise it, Phymatolithon calcareum ( Rhodolith bed integrity is threatened by human activities (Kamenos et al., 2003). The loss of habitat heterogeneity and habitat degradation may impact their functioning (Kamenos et al., 2003). In the past, rhodolith beds were exploited as a source of calcareous sediment to be used in agriculture (Birkett et al., 1998) and by bottom-fishing practices Tauran et al., 2020). ...
Article
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Maerl beds are biogenic benthic habitats distributed worldwide and known to sustain high productivity and biodiversity levels. In the Mediterranean, the number of studies that have been carried out is limited, and little is known on its real distribution, mostly due to the difficulties of exploring such habitats -Due to the high transparency of Mediterranean waters, maerl can be found at depths of over 50 m making mandatory the use of benthic grabs and ROVs. The last published data from Maltese waters were taken two decades ago. In this present study, we provide new insights on this poorly known habitat, in particular regarding the north western bank, designated as a NATURA 2000 protected area, in which human activities are also carried out, such as blue fin tuna ranching. The objective of this work is to provide information regarding this delicate habitat, especially relevant for future management plans and authorities.
... The loose open structure of maerl coralline algae, including the species Lithothamnion corallioides, Lithothamnion glaciale and Phymatolithon calcareum, provides habitat and refugia for a very wide range of organisms such that maerl beds typically have very high diversity [36,395,446]. Maerl beds are often formed in association with sand and gravel and can constitute both live and dead maerl thalli [447,448]. Maerl habitats exhibit a high heterogeneity compared to the surrounding substrata [36,447]. Maerl is also important in calcium carbonate cycling, providing grains for coastal habitats, especially beaches and dunes [449]. ...
... Maerl beds are often formed in association with sand and gravel and can constitute both live and dead maerl thalli [447,448]. Maerl habitats exhibit a high heterogeneity compared to the surrounding substrata [36,447]. Maerl is also important in calcium carbonate cycling, providing grains for coastal habitats, especially beaches and dunes [449]. ...
Technical Report
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The Marine and Coastal Access Act 2009 created a new type of Marine Protected Area (MPA), called a Marine Conservation Zone (MCZ). MCZs, together with other types of existing MPAs, will deliver the Government’s aim for the formation of an ‘ecologically coherent network of well managed Marine Protected Areas’. Through stakeholder engagement and consultation the Department for Food and Rural Affairs (Defra) has developed seven design principles which are to be applied to the UK network of MPAs; o Representativity o Replication o Viability o Adequacy o Connectivity o Protection o Best available evidence The objective of this study is to address the design principle of viability through the assessment of 37 species and 25 habitats which are likely to be protected by the MPA network (known as features of conservation importance – FOCI). A viable MPA has been defined within the scope of this study as being an area large enough to encompass most naturally occurring ecological processes and the home ranges of the species or groups of species characteristic of habitat communities which are the target for protection. The specific objectives of this viability assessment were to review existing literature to identify adult home ranges for species of conservation importance and to identify the minimum site area required for each habitat of conservation importance. This review focused on published peer reviewed journal articles but where gaps exist, was supplemented with data and reports produced by Marine Ecological Surveys Ltd as well as other grey literature. As most species in this review are sessile or sedentary the reviews consider several factors other than home range, important to the ecology, and hence viability of species and habitats.
... One of the consequences of playing host to such great biodiversity is that maërl beds experience high levels of fishing impacts (e.g. dredging and trawling), as beds are fished for valuable commercial species (Bordehore, Ramos-Esplá, & Riosmena-Rodríguez, 2003;de Grave & Whitaker, 1999;Hauton, Hall-Spencer, & Moore, 2003), and few studies have assessed fishing effects based on a comparison of control (unfished) vs affected sites (fished) (Hall-Spencer & Moore, 2000; Kamenos et al., 2003). Regardless of the design, all these studies found that mobile fishing gears have important impacts on maërl beds in terms of the loss of live cover in the study area) and structure (e.g. ...
... Regardless of the design, all these studies found that mobile fishing gears have important impacts on maërl beds in terms of the loss of live cover in the study area) and structure (e.g. complexity-heterogeneity; Hall-Spencer & Moore, 2000; Kamenos et al., 2003). In addition, the mechanical action of bottom trawl-gear causes abrasion and contributes to the extraction, burial and breakage of thalli Hall-Spencer & Moore, 2000) and fragmentation and dispersion of rhodoliths, with implications for the reduction of size-structure at the community level (de Grave & Whitaker, 1999;Hall-Spencer & Moore, 2000). ...
Article
Maërl is a benthic community composed of accumulations of coralline red algae with an essential eco-biological role in marine ecosystems. This low-resilience community has acquired a high conservation status as many anthropogenic impacts threaten this globally distributed ecosystem. Some of the potentially more important but less studied impacts are those caused by fishing activities due to the lack of proper controls. This study investigates the potential fishing impacts and depth-related differences on the rhodolith morpho-demographic traits of two maërl-forming algae, Lithothamnion corallioides and Spongites fruticulosus, with distinct morphologies (ramified vs nucleated). Rhodolith size and shape (roundness and solidity) indicators were assessed in maërl beds protected from fishing inside a large 25-year old no-take MPA, in a contiguous 6-year no-take zone, and in adjacent fished beds. Rhodoliths of both species were bigger, rounder (spherical) and more solid (structurally less complex) in shallow than in deep beds of the long-term protected area, which was probably a result of a more active hydrodynamic regime and higher irradiance in shallow beds. Fishing effects manifested differently depending on the morphological properties of rhodoliths, which resulted in a decrease in size and complexity in L. corallioides and roundness in S. fruticulosus. Such fishing impacts were significant only inside the short-term 6-year protected area. The most plausible cause of this unexpected observation is the highly localized trammel-net fishing effort with long soak-times along the boundary of the contiguous 25-year MPA, where before closure, fishing effort was concentrated in expectation of greater catches from spillover (i.e. fishing the line). This is the first study to document the impacts of fishing the line on structural species and indicates that boundaries of successful MPAs could be zones of maximum disturbance, a fact that should be taken into account in management conservation decisions.
... Maerl was not treated separately as a result of its gravel−pebble-sized form around South Arran. Furthermore, impacted maerl has been demonstrated to be more similar to gravel than live maerl (Kamenos et al. 2003). ...
Article
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The protection of species requires an understanding of their habitat requirements and how habitat characteristics affect their distribution, survival and growth. This need is especially important in areas where anthropogenic pressures can not only have a significant direct impact on the survival of the species but also damage their habitat. The Firth of Clyde in southwestern Scotland was an important commercial fishing area for a variety of demersal fish species up until 1973. However, stocks rapidly declined thereafter and the catch of targeted species ceased in 2005, despite fisheries measures put in place to aid recovery. Changes in the availability and quality of fish habitat are possible explanations for this lack of recovery. Here, we report on stereo baited remote underwater video surveys in the Firth of Clyde between June and September in 2013 and 2014 to determine the habitat of juvenile Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus and whiting Merlangius merlangus. Habitat predictor variables explored included substratum type, depth, wave fetch, and epibenthic and demersal fauna diversity. G. morhua were most abundant in shallow, sheltered areas composed of gravel-pebble containing maerl. M. aeglefinus and M. merlangus predominated over deeper sand and mud. Ontogenetic shifts in all 3 species were also observed. Relative abundances of G. morhua and M. merlangus were positively related to the diversity of epibenthic and demersal fauna. Our results indicate that spatial conservation measures to benefit demersal fish should be advised by patterns of epibenthic and demersal fauna diversity as well as physical substratum types.
... Maë rl beds have a worldwide distribution (Foster 2001) and comprise different species and growth forms (Bosence 1983b, Riosmena-Rodríguez et al. 1999, Grall 2003. These maë rl communities are threatened by direct exploitation and anthropogenic impacts and their recovery potential is poor (Grall and Glé marec 1997, IMPACT 1998, De Grave et al. 2000, Hall-Spencer and Moore 2000, Barberá et al. 2003, Grall 2003, Kamenos et al. 2003, Wilson et al. 2004, OSPAR Commission 2006. ...
Article
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We studied the conservation status of a maërl bed off Benencia Island (NW Spain) over a 2-year period using SCUBA and dredging. The maërl bed, which includes a maërl beach, extended from the intertidal to subtidal zones (18 m), and occupied an area of 215 ha. It was composed of a pure unattached coralline algal deposit occasionally mixed with broken shells. The area estimated for the highest maërl cover (76-100%) was greater than reported in previous research. The living maërl layer reached 15 cm in depth and the living/dead maërl ratio was high (80-100% living maërl cover). The dominant maërl-forming species was Phymatolithon calcareum, although unattached plants of Mesophyllum sp. reaching 10 cm in diameter were found in two sites. Both maërl species are fruticose. The proportion of discoidal specimens of P. calcareum was related to depth. The associated flora comprised 137 species whose seasonal variations were very marked, with high floristic richness in summer (71 species) and low in winter (35 species). Crustose and turf-like species were the dominant floral components throughout the year, whereas the presence of other species was restricted to specific periods. We propose that Benencia Island be included in future Atlantic Iberian maërl bed conservation schemes.
... In the Mediterranean Sea, together with Posidonia meadows, coralligenous and vermetid bioconstructions, they are considered as extremely biodiverse benthic habitats of high conservation and economic value (Ballesteros E., 2006;Basso et al., 2016;Franzese et al., 2017;Vassallo et al., 2017;Donnarumma et al., 2018;Buonocore et al., 2018Buonocore et al., , 2019Buonocore et al., , 2020aBuonocore et al., , 2020b, supporting a high diversity of associated species, some of which are commercially important (Soto, 1990;Mannino et al., 2002;Castriota et al., 2003Castriota et al., , 2005Templado et al., 2002;Hall-Spencer et al., 2003). These habitats are often affected by degradation and loss of structural heterogeneity due to anthropogenic disturbances, at both global scale, such as climate change, which will likely impact coralline algae in the near future (Ragazzola et al., 2012(Ragazzola et al., , 2016Donnarumma et al., 2014;Rendina et al., 2019;Rindi et al., 2019), and local one, such as fishing activities, that causes mechanical impact and sediment accumulation (Marrack, 1999;Bordehore et al., 2000Bordehore et al., , 2003Kamenos et al., 2003;Foster et al., 2013). In fact, despite their hard carbonate thallus, rhodoliths are often fragile (particularly mäerl forming species), and with low growth rates, of the order of just 1 mm year -1 (also depending on the coralline alga species, and the light intensity and temperature; Blake and Maggs, 2003;Martin and Gattuso, 2009;Foster et al., 2013). ...
Article
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Impact of fishing gears and marine litter is a recognized global socio-ecological issue. Little is known about the extent of the problem in the Mediterranean seabed; even less information is available regarding litter distribution and its effects on deep rhodolith beds. Indeed, Mediterranean rhodolith beds are often remote and not yet sufficiently explored habitats, despite being internationally protected and recognized among the most important benthic communities for biodiversity maintenance. In this study, a quantitative assessment of marine litter and lost fishing gears, observed using a remotely operated vehicle, was carried out in 6 sites off the Campania Coast (Tyrrhenian Sea) characterized by different rhodolith covers. A negative correlation between abundance and richness of both marine litter and abandoned fishing gears with respect to the rhodolith cover was detected, suggesting that indirect human pressure along the coasts and direct effect of fishing activities might negatively damage these habitats. In fact, a lot of abandoned fishing gears and litter were recorded in all the 4 sites of the Gulf of Naples, confirming the high impact of maritime activities in this overcrowded area. Particularly, the Secchitiello site showed a very low mean cover of rhodoliths (<5%) in concurrence with the highest abundance of lost fishing gears and litter. On the contrary, the lowest abundance of fishing gears and litter was recorded in the 2 sites along the Cilento coast, possibly due to the relatively low maritime activities in this poorly inhabited area. In conclusion, this work gives new insights into the anthropic pressure due to marine litter and fishing on deep Mediterranean rhodolith beds, and provides useful data for their management and conservation.
... RBs are threatened by habitat degradation and loss of structural heterogeneity due to anthropogenic impacts, which can hamper the functioning of these habitats [26]. Rhodoliths are often fragile (particularly unattached branches), and their growth rate is on the order of 1 mm year −1 , also depending on environmental factors as light and temperature [4,24,27]. ...
Article
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Rhodolith beds (RBs) are bioconstructions characterized by coralline algae, which provide habitat for several associated species. Mediterranean RBs are usually located in the mesophotic zone (below 40 m), and thus are frequently remote and unexplored. Recently, the importance and vulnerability of these habitats have been recognized by the European Community and more attention has been drawn to their investigation and conservation. This study reports the results of an extensive monitoring program, carried out within the Marine Strategy Framework Directive (2008/56/EC), in six sites off the Campania coast (Italy, Mediterranean Sea). New insights were given into the distribution, cover, vitality (i.e., live/dead rhodolith ratio), structural complexity, and coralline algae composition of RBs. Remotely operated vehicles (ROV) investigations allowed the description of several RBs, and the discovery of a RB with rhodolith cover >65% offshore the Capri Island. Only two sites (Secchitiello and Punta Campanella) showed a very low mean cover of live rhodoliths (<10%); hence, not being classifiable as RBs. The collected rhodoliths were mostly small pralines (~2 cm), spheroidal to ellipsoidal, with growth-forms ranging from encrusting/warty to fruticose/lumpy. Coralline algae identification revealed a high diversity within each bed, with a total of 13 identified taxa. The genus Lithothamnion dominated all sites, and Phymatolithon calcareum and Lithothamnion corallioides, protected by the Habitats Directive (92/43/EEC), were detected in all RBs.
... However, maerl beds are fragile and very slow growing, often taking thousands of years to build up, meaning they are exceptionally vulnerable to damage by scallop dredging (Giraud & Cabioch 1976;Foster 2001;Grall & Hall-Spencer 2003). A single impaction event with a scallop dredge can significantly reduce the structural complexity of a maerl bed by breakage, and can kill the maerl by burying it under sediment (Hall-Spencer & Moore 2000; Kamenos et al. 2003). For example, a study off the west coast of Scotland found that a single tow of three scallop dredges crushed and compacted maerl beds and buried the maerl 8 cm below the sediment surface (Hall-Spencer & Moore 2000). ...
Technical Report
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The king scallop fishery is the fastest growing fishery in the UK and currently the second most valuable. The UK is also home to the largest queen scallop fishery out of all of Europe. However, concerns have been raised about the effects of this recent growth of UK scallop fisheries among scientists and conservation bodies, as well as amongst the public following recent media campaigns (e.g. Hugh’s Fish Fight). This is because the majority of scallop landings (95%) are made by vessels towing scallop dredges, a type of fishing gear known to cause substantial environmental impacts. In addition, several scallop stocks are showing signs of overexploitation and there is concern over future impacts of ocean warming and acidification. Although, there have been several recent improvements in the management of scallop fisheries in parts of the UK, information on many scallop stocks around the UK is still lacking. This report therefore proposes that better monitoring and stock assessments are needed for these scallop fisheries and stocks. With recent legislation soon to result in the development of a new network of marine protected areas (MPAs) around the UK, and improved management of fisheries in European Marine Sites, now is a crucial time to review the UK scallop dredge fishery and its impacts on the wider environment so that this new legislation can support a sustainable future for the UK scallop fishery. This report was therefore commissioned by the Sustainable Inshore Fisheries Trust with the aim of collating existing knowledge on the management and environmental impacts of scallop fisheries around the UK.
... Demersal gear deposits sediment over a wide area around fished tracks and suspension feeders suffer from clogged gills, while algae are smothered. Kamenos et al. (2003) looked at the heterogeneity of substrates in dredged v. undredged rhodolith beds and found unimpacted beds had higher structural heterogeneity, and that much of the rhodolith bed was killed post-burial by a lack of light. Similar results are reported by Bordehore et al. (2003) examining the impacts of otter trawling on rhodolith beds in Spain, and by Riul et al. (2008) who observed decreases in primary production of up to 70% when rhodoliths were buried by a thin sediment layer. ...
Article
Calcified macroalgae are distributed in marine habitats from polar to tropical latitudes and from intertidal shores to the deepest reaches of the euphotic zone. These algae play critical ecological roles including being key to a range of invertebrate recruitment processes, functioning as autogenic ecosystem engineers through provision of three-dimensional habitat structure, as well as contributing critical structural strength in coral reef ecosystems. Calcified macroalgae contribute significantly to the deposition of carbonates in coastal environments. These organisms are vulnerable to human-induced changes resulting from land and coastal development, such as altered patterns of sedimentation, nutrient enrichment through sewage and agricultural run-off, and are affected by coastal dredging and aquaculture. The consequences of increasing sea surface temperatures and fundamental changes in the carbon chemistry of seawater due to CO2 emissions from anthropogenic activities will have serious impacts on calcifying macroalgae. It is not yet understood how interactions between a range of variables acting at local and global scales will influence the viability of calcifying macroalgae and associated ecosystems. Research is urgently needed on all aspects of the taxonomy, biology and functional ecology of calcifying macroalgae. Without an understanding of the species present, measurement of change and understanding species-specific responses will not be possible.
... Maerl appears to be a group that is especially sensitive to disturbance. A comparison between dredged and un-dredged ('pristine') maerl beds found that dredged areas had a reduced structural complexity, resembling more a gravel bottom in structure than live maerl (Kamenos et al. 2003). Even a single pass of towed gear can bury maerl under sediment, killing it through lack of light (Hall-Spencer & Moore 2000). ...
... Maërl reproduces by fragmentation of thalli during vegetative propagation, as well as by the production of spores ( Birkett et al. 1998;Mitchell 2001). Maërl beds support high biodiversity and an abundance of rare epifauna and epiflora (Keegan 1974;Maggs 1983;Kamenos et al. 2003). They are important nursery grounds for juvenile stages of mollusks, crustaceans, and commercially important fish (HallSpencer 1998;Kamenos et al. 2004). ...
Article
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The importance of a grain-size-dependent shape metric, convexity, for determining the unusual settling velocity characteristics of maërl, a variety of unattached coralline algae, has been quantified by modeling of settling-tube data. A modification of the general settling-velocity equation of Ferguson and Church (2004), involving a dependence of the drag coefficient-related constant, C2, on grain size, produces a satisfactory fit to the experimental observations. For a given grain size and at Reynolds numbers greater than ∼ 220, maërl grains experience greater drag than is predicted for natural quartz grains by Ferguson and Church (2004) because of this grain-size-dependent roughness. Subsequent detailed measurements of maërl grain shape using microscopic image analysis confirm a strong positive linear relationship between grain roughness, quantified by the reciprocal of convexity, and grain size. This departure from the ideal settling characteristics of siliciclastic gravel is hypothesized to explain the observed propensity of maërl, under suitable hydrodynamic conditions, to form beach deposits with a low percentage of sand. Maërl samples from three different sedimentary environments (open marine, intertidal, and beach) exhibit different linear relationships between roughness and grain size, probably resulting from different degrees of abrasion due to a combination of different wave climates and transport histories. This spatial variability in grain texture suggests that a general equation for maërl settling velocity is not possible. However, for maërl, and other branched sediment types, it may only be necessary to measure the convexity of the middle and largest size fractions to estimate the linear variation of C2 with grain size, resulting in an accurate estimate of the settling-velocity curve. In the broader context of physical sedimentology, our results indicate that, over a range of bottom current conditions between 200 and 250 mm s−1, where the settling curve of maërl is flat and grain-size invariant relative to siliciclastic sediment, a larger part of the maërl grain-size distribution can remain in suspension compared to the siliciclastic sediment. This contrast in physical properties may be an effective process for the spatial separation of coarse siliciclastic and biogenic sediment.
... Rhodolith beds form complex habitats that support a high diversity of invertebrates, fish and algae (Steller et al. 2003;Copeland et al. 2008;Hernandez-Kantun et al. 2017 and references therein) and also provide refuge and feeding grounds for commercially important species such as juvenile Atlantic cod (Kamenos et al. 2004) and juvenile Icelandic scallop (Copeland 2006). Rhodolith beds are sensitive to bottom contact fishing activities (Hall-Spencer and Moore 2000; Kamenos et al. 2003), waste build-up from aquaculture operations (Hall-Spencer et al. 2006) and are particularly vulnerable to impacts from ocean acidification (Martin and Hall-Spencer 2017 and references therein). The rhodolith bed in Newman Sound is also in close proximity to sizeable eelgrass (Zostera marina) beds located in the inner sound (Rao et al. 2014). ...
Article
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As human impacts continue to threaten coastal habitats and ecosystems, marine benthic habitat and substrate mapping has become a key component of many conservation and management initiatives. Understanding the composition and extent of marine habitats can inform marine protected area (MPA) planning and monitoring, help identify vulnerable or rare habitats and support fisheries management. To support conservation planning in Eastern Canada, we mapped the seafloor of Newman Sound, identifying the benthoscape classes (i.e. discrete biophysical seafloor classes) of this ecologically diverse and unique fjord in Newfoundland and Labrador (NL). Mapping was achieved using multibeam echosounder (MBES) data collected using multiple platforms, seafloor videos and an unsupervised pixel-based classification method. Seven benthoscape classes were identified within the extent of the MBES coverages. Multivariate statistical analyses indicate that two benthoscape classes - mixed boulder and mud - support distinct epifaunal communities, and also capture the changes in benthic community composition between hard/shallow substrates and soft/deep substrates. Our results illustrate how benthoscape maps can inform marine spatial planning and conservation in the Newman Sound region, support monitoring and also calls for adaptive management of the adjacent Eastport MPA.
... Although plant size and branch density can vary by depth, among and within beds (Steller and Foster, 1995), and over time, our direct field observations indicate fishing activity likely contributes to rhodolith fragmentation as well as mortality. Similarly, Kamenos et al. (2003) reported fishing gear dragged on live rhodolith beds can affect substratum heterogeneity, reducing rhodolith habitat to areas more closely resembling gravel bottoms. Additionally, Bordehore et al. (2003) observed that rhodolith cover and maximum size were four and two times greater at a marine reserve than in a frequently trawled area, respectively. ...
Article
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The most basic level of artisanal fisheries is represented by hand-collecting, which is highly selective and widely recognized as having minimal impact on the environment. Nevertheless, there are some concerns that hand-collecting fisheries have the potential to negatively affect marine environments. We assessed the potential impacts of hookah diving for the pen shell Atrina maura, a hand-collecting fishery, in the Gulf of California, México. In situ observations revealed high sediment resuspension and Atrina shell remains widespread on the rhodolith bed where they are collected (‘fishery’ site), and on a nearby shallow sedimentary habitat where fishermen dump empty shells and tissue remains (‘polluted’ site). Structural complexity (i.e. size, shape and degree of branching) of rhodoliths at the fishery site were lower than previous reports in the area, while high mud and organic matter content was characteristic of the polluted site. Comparisons of faunal samples at the polluted site and control site showed that while faunal density and taxa abundance was greater at the polluted site, taxa evenness and Shannon's diversity indices were greater at the control site. Faunal abundance was highest for detritivorous gastropods (e.g. Cerithiidae, Caecidae) and bivalves tolerant to muddy substrata with potential low oxygen conditions (e.g.Thyasiridae), as well as deposit-feeding polychaetes (e.g. Flabelligeridae, Cirratulidae) at the polluted site. This study suggests impacts of artisanal hand-collecting fisheries on the benthos can be more severe than previously assumed and highlights the need to devise and implement adequate fishing education and management programs to protect benthic resources and the livelihood of local fishermen.
... Assessing changes in habitat complexity and architecture of maerl beds clearly constitutes a challenging task. Up to now, aside from purely qualitative assessments 5,21 , studies focusing on beds architecture have used fastidious and time-consuming ex-situ measurements involving both destructive sampling and artificial rearrangements of thalli 22 . In this context, the use of Sediment Profile Imagery (SPI) techniques 26 in maerl beds is likely to allow for a non-destructive in-situ acquisition of cross-section images of maerl bed and thus for the easy assessment of their vertical architecture and structural characteristics. ...
Article
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Maerl beds form complex biogenic benthic habitats, characterized by high productivity as well as diverse biological communities. Disturbances associated with extraction and/or fishing activities using mobile bottom-contacting gears such as clam-dredges induce the most severe and long-term effects on these fragile habitats. We here investigated the effects of dredge-fishing on maerl in the bay of Brest (France). We quantified maerl beds structure and vitality across a fine scale quantified dredging intensity gradient through the acquisition of in-situ images of beds cross-section using Sediment Profile Imaging system (SPI). Declines in the proxies of maerl vitality and habitat complexity were measured across the gradient, and were associated with significant changes in the vertical distribution of live and dead maerl as well as of interstitial space. Fishing with dredges caused maerl mortality, substratum compaction, and decreasing habitat complexity. SPI imaging techniques also allowed for an assessment of changes in spatial heterogeneity that dredging created on several aspects of the structure and vitality of maerl beds. It suggests that direct and indirect disturbances induced by dredging are not acting at the same spatial scale, and can thereby differentially affect the ecosystem functions linked to vitality and habitat complexity.
... In the long term, these effects should increase the numbers of juvenile scallops entering the adult stock as a greater proportion of juveniles survive to reach maturity (Beukers-Stewart et al., 2003;Vause et al., 2007). It is interesting that live maerl was over 300% more abundant within the reserve, as evidence suggests that recovery of maerl beds should take several decades, due to their extremely slow growth (Foster, 2001;Giraud and Cabioch, 1976;Grall and Hall-Spencer, 2003;Hall-Spencer and Moore, 2000;Kamenos et al., 2003). As the abundance of live maerl showed no clear signs of increasing over the study period, the greater levels of maerl within the reserve may just be an artefact of maerl being more prevalent within the reserve than outside prior to its establishment. ...
... In the long term, these effects should increase the numbers of juvenile scallops entering the adult stock as a greater proportion of juveniles survive to reach maturity (Beukers-Stewart et al., 2003;Vause et al., 2007). It is interesting that live maerl was over 300% more abundant within the reserve, as evidence suggests that recovery of maerl beds should take several decades, due to their extremely slow growth (Foster, 2001;Giraud and Cabioch, 1976;Grall and Hall-Spencer, 2003;Hall-Spencer and Moore, 2000;Kamenos et al., 2003). As the abundance of live maerl showed no clear signs of increasing over the study period, the greater levels of maerl within the reserve may just be an artefact of maerl being more prevalent within the reserve than outside prior to its establishment. ...
... Maë rl beds have a worldwide distribution (Foster 2001) and comprise different species and growth forms (Bosence 1983b, Riosmena-Rodríguez et al. 1999, Grall 2003. These maë rl communities are threatened by direct exploitation and anthropogenic impacts and their recovery potential is poor (Grall and Glé marec 1997, IMPACT 1998, De Grave et al. 2000, Hall-Spencer and Moore 2000, Barberá et al. 2003, Grall 2003, Kamenos et al. 2003, Wilson et al. 2004, OSPAR Commission 2006. ...
... To date, studies comparing maerl beds with adjacent bare sediments have focused on the importance of the maerl structure for local benthic biodiversity (Barbera et al. 2003, Kamenos et al. 2003, Teichert 2014. No previous studies have compared the biogeochemical functioning of the maerl bed to adjacent bare sediments. ...
Article
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Coralline algal (maerl) beds are widespread, slow-growing, structurally complex perennial habitats that support a high biodiversity, yet when compared to seagrass beds or kelp forests they are significantly understudied. We present the first eddy covariance (EC) study on a live maerl bed to assess the community benthic gross primary productivity (GPP), respiration (R), and net ecosystem metabolism (NEM) derived from diel EC time series collected during 5 seasonal measurement campaigns in temperate Loch Sween, Scotland. Measurements were also carried out at an adjacent (~20 m apart) permeable sandy habitat. The O2 exchange rate was highly dynamic, driven by light availability and the ambient tidally-driven flow velocity. Linear relationships between the EC O2 fluxes and available light indicate that the benthic phototrophic communities were light-limited. The compensation irradiance (Ec) varied seasonally and was typically ~1.8 times lower at the maerl bed compared to the sand. A substantial GPP was evident at both sites; however, the maerl bed and the sand habitat were net heterotrophic during each sampling campaign. Additional inputs of carbon (C) of ~4 mol m-2 yr-1 at the maerl bed and ~7 mol m-2 yr-1 at the sand site were required to sustain the benthic O2 demand. Parallel deployment of 0.1 m2 benthic chambers during night-time resolved O2 uptake rates that varied by up to ~8 times between replicate chambers (from -0.4 to -3.0 mmol O2 m-2 h-1; n=4). However, despite extensive O2 flux variability on meter horizontal scales, mean rates of O2 uptake as resolved in parallel by chambers and EC were typically within 20% of one another.
... Maerl beds are fragile and very slow growing, often taking thousands of years to build up, which means they are exceptionally vulnerable to damage by scallop dredging (Giraud and Cabioch, 1976;Foster, 2001;Grall and Hall-Spencer, 2003;Newell and Woodcock, 2013). A single impaction event with a scallop dredge can significantly reduce the structural complexity of a maerl bed by breakage and can kill the maerl by burying it under sediment (Hall-Spencer and Moore, 2000; Kamenos et al., 2003). For example, a study off the west coast of Scotland found that a single tow of three scallop dredges crushed and compacted maerl beds, and buried the maerl 8 cm below the sediment surface (Hall-Spencer and Moore, 2000). ...
Chapter
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Global landings of scallops have grown dramatically in recent decades and these fisheries are now among the most lucrative in several countries around the world. Despite this apparent success story, concerns have arisen about the wider ecosystem effects of scallop fisheries. This is particularly the case for the most common type of fisheries that use dredges to rake scallops off the seafloor. Here the evidence for negative effects arising from this practice is reviewed and suggestions offered as to ways in which scallop fisheries might be better managed. In general, dredging causes loss of biodiversity and reduces the complexity of benthic habitats by flattening substrates and removing structurally complex species such as hydroids, bryozoans and seaweeds. This is significant because such habitats are key nursery and feeding areas for a wide range of species, including commercially important fish and shellfish. Scallop dredging also catches a variety of more mobile species such as crustaceans, echinoderms, fishes, and in certain areas, sea turtles, which is clearly of concern. Despite these general rules, the magnitude of effects varies considerably in different habitats. The most severe are in biogenic reefs such as formed by maerl and mussels, so there is a strong argument for fully protecting such areas. Reef and cobble habitats also appear relatively susceptible, but soft sediments such as sand, mud and gravel (which are the focus of most scallop fisheries) appear more resilient, particularly in areas adapted to high levels of natural disturbance. Determining the full effects of dredging remains difficult, however, because most fishing grounds have been exploited for decades, long before scientific study began. Long-term protected areas are beginning to provide insights into the recovery and composition of benthic communities in the absence of dredging. Continued study of these areas will be a key to gaining a better understanding in the future. In terms of reducing the ecosystem effects of dredging, an approach that combines effort control, gear modifications, and spatial management is suggested. Spatial management is showing great promise where it has been applied as it can offer a win–win scenario, which protects vulnerable habitats while boosting scallop stocks by providing breeding and nursery refuges; however, spatial management must be carefully planned to maximise biological benefits while accounting for socio-economic factors. Scallop fisheries must also be managed in unison with other fisheries in order to restore diversity and resilience to oceans facing an uncertain future of climate change and growing anthropogenic pressure.
... For example, substratum height, height variation, and interstitial space will affect the rugosity, while diversity of substratum composition, areal extent, and spatial distribution will affect the heterogeneity (Gratwicke & Speight 2005. It is also important to be aware that substrata and community composition of the habitat may vary over time following successional processes or anthropogenic impacts (Sale 1991, Friedlander & Parrish 1998b, Kamenos et al. 2003. Table 1 gives some examples of methodological studies in which substratum rugosity and heterogeneity have been measured. ...
Chapter
Fishing and other anthropogenic impacts have led to declines in many fish stocks and modification of the seabed. As a result, efforts to restore marine ecosystems have become increasingly focused on spatially explicit management methods to protect fish and the habitats they require for survival. This has led to a proliferation of investigations trying to map 'habitats' vulnerable to anthropogenic impacts and identify fish resource requirements to meet conservation and management needs. A wide range of habitat-related concepts, with different uses and understandings of the word 'habitat' itself has arisen as a consequence. Inconsistencies in terminology can cause confusion between studies, making it difficult to investigate and understand the ecology of fish and the factors that affect their survival. Ultimately, the inability to discern the relationships between fish and their environment clearly can hinder conservation and management measures for fish populations. This review identifies and addresses the present ambiguity surrounding definitions of habitat and habitat-related concepts currently used in spatial management of demersal marine fish populations. The role of spatial and temporal scales is considered, in addition to examples of how to assess fish habitat for conservation and management purposes. © 2016 by R.N. Hughes, D.J. Hughes, I.P. Smith, A.C. Dale. All rights reserved.
... For example, substratum height, height variation, and interstitial space will affect the rugosity, while diversity of substratum composition, areal extent, and spatial distribution will affect the heterogeneity (Gratwicke & Speight 2005. It is also important to be aware that substrata and community composition of the habitat may vary over time following successional processes or anthropogenic impacts (Sale 1991, Friedlander & Parrish 1998b, Kamenos et al. 2003. Table 1 gives some examples of methodological studies in which substratum rugosity and heterogeneity have been measured. ...
Chapter
Fishing and other anthropogenic impacts have led to declines in many fish stocks and modification of the seabed. As a result, efforts to restore marine ecosystems have become increasingly focused on spatially explicit management methods to protect fish and the habitats they require for survival. This has led to a proliferation of investigations trying to map ‘habitats’ vulnerable to anthropogenic impacts and identify fish resource requirements to meet conservation and management needs. A wide range of habitat-related concepts, with different uses and understandings of the word ‘habitat’ itself has arisen as a consequence. Inconsistencies in terminology can cause confusion between studies, making it difficult to investigate and understand the ecology of fish and the factors that affect their survival. Ultimately, the inability to discern the relationships between fish and their environment clearly can hinder conservation and management measures for fish populations. This review identifies and addresses the present ambiguity surrounding definitions of habitat and habitat related concepts currently used in spatial management of demersal marine fish populations. The role of spatial and temporal scales is considered, in addition to examples of how to assess fish habitat for conservation and management purposes.
... However, towed fishing gear (e.g. trawling) can easily damage rhodoliths (maerl; Hall-Spencer and Moore, 2000; Kamenos and Moore, 2003). Overall, coralline algal distribution is likely primarily determined by irradiance and temperature (Adey and McKibbin, 1970; Adey and Adey, 1973; Gattuso et al., 2006). ...
Article
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The ongoing increase in anthropogenic carbon dioxide (CO2) emissions is changing the global marine environment and is causing warming and acidification of the oceans. Reduction of CO2 to a sustainable level is required to avoid further marine change. Many studies investigate the potential of marine carbon sinks (e.g. seagrass) to mitigate anthropogenic emissions, however, information on storage by coralline algae and the beds they create is scant. Calcifying photosynthetic organisms, including coralline algae, can act as a CO2 sink via photosynthesis and CaCO3 dissolution and act as a CO2 source during respiration and CaCO3 production on short-term timescales. Long-term carbon storage potential might come from the accumulation of coralline algae deposits over geological timescales. Here, the carbon storage potential of coralline algae is assessed using meta-analysis of their global organic and inorganic carbon production and the processes involved in this metabolism. Net organic and inorganic production were estimated at 330 g C m−2 yr−1 and 900 g CaCO3 m−2 yr−1 respectively giving global organic/inorganic C production of 0.7/1.8 × 109 t C yr−1. Calcium carbonate production by free-living/crustose coralline algae (CCA) corresponded to a sediment accretion of 70/450 mm kyr−1. Using this potential carbon storage for coralline algae, the global production of free-living algae/CCA was 0.4/1.2 × 109 t C yr−1 suggesting a total potential carbon sink of 1.6 × 109 tonnes per year. Coralline algae therefore have production rates similar to mangroves, salt marshes and seagrasses representing an as yet unquantified but significant carbon store, however, further empirical investigations are needed to determine the dynamics and stability of that store.
... Equally, maerl was not treated separately from gravel-pebble substratum type because of its gravel-pebble sized form around south of Arran. In addition impacted maerl has been demonstrated to be more similar to gravel than live maerl (Kamenos et al. 2003). As a result of insufficient prior knowledge of the substratum types of the area, the experimental design was unbalanced. ...
... University of Maryland Center for Environmental Science. (Sainsbury et al., 1997;Auster et al., 1996), mussel beds (Veale et al., 2000;Hiscock et al., 2005;Wolff, 2005), file shell reefs (Kaiser et al., 1999;Hall-Spencer and Moore, 2000;Kamenos et al., 2003), oyster bars (Rothschild et al., 1994), rocks, large cobbles, and boulders (Kaiser et al., 2000;Guidetti et al., 2003;Sewell et al., 2007), and deep coral reefs Etnoyer and Morgan, 2003;Freiwald et al., 2004). Less complex habitats such as sand waves or burrows may also be affected by the passage of the fishing gear over the seabed; nevertheless, the impacts on these sediment features are lower than in structurally more complex habitats. ...
Chapter
The present chapter provides a brief review of the main impacts on coastal marine ecosystems resulting from fisheries and aquaculture activities. It covers a wide range of topics, including habitat degradation, fragmentation, and loss; changes in biodiversity, food webs, and trophic interactions; loss of genetic diversity; and spread of parasites and diseases. A number of worldwide case studies on mitigation measures are presented, providing examples of best practices aiming to reduce impacts on coastal marine environments. Several restoration initiatives are also described based on selected case studies. Finally, the importance of restoration methods, as ecohydrology, based on a holistic approach to manage ecosystems and revert degradation, is highlighted.
... In the Gulf of California, beds containing rhodoliths with larger branching densities and thallus volumes had higher abundances and diversity of cryptofauna (Steller et al., 2003). From assessment of maerl beds exposed to dredging we can infer that smaller rhodoliths will lead to a decrease in habitat complexity (Kamenos et al., 2003). Studies on temperate marine habitats have revealed that a loss in habitat complexity has led to a decrease in species richness and abundance (Airoldi et al., 2008). ...
Article
The structure (both gross morphology and internal cellular) of rhodoliths (free-living forms of coralline algae) are important factors in the ability of rhodoliths to create complex habitats. Using Finite Element Analysis, models of the internal structure of rhodoliths have been interrogated to assess how changes to the cellular structure affect structural integrity. These models are accurate in their portrayal of the internal skeleton, yet they fail in other ways. Specifically, they lack accurate environmental loads and material properties (Young's modulus), which form the basis of an accurate quantification of the structural integrity of rhodoliths. Here we measure the material properties of rhodoliths and quantify the hydrodynamic forces acting on them. Applying correct material properties and hydrodynamic forces, our results show that rhodoliths experience larger stresses than previously modelled. Water velocities representing storm surges cause internal stresses exceeding experimentally derived breakage stresses. As the intensity and frequency of storm surges are predicted to increase, the forces generated by them will result in breakage and hence affect their role as habitat builders.
... For example, substratum height, height variation, and interstitial space will affect the rugosity, while diversity of substratum composition, areal extent, and spatial distribution will affect the heterogeneity (Gratwicke & Speight 2005. It is also important to be aware that substrata and community composition of the habitat may vary over time following successional processes or anthropogenic impacts (Sale 1991, Friedlander & Parrish 1998b, Kamenos et al. 2003. Table 1 gives some examples of methodological studies in which substratum rugosity and heterogeneity have been measured. ...
Article
Full-text available
Fishing and other anthropogenic impacts have led to declines in many fish stocks and modification of the seabed. As a result, efforts to restore marine ecosystems have become increasingly focused on spatially explicit management methods to protect fish and the habitats they require for survival. This has led to a proliferation of investigations trying to map ‘habitats’ vulnerable to anthropogenic impacts and identify fish resource requirements to meet conservation and management needs. A wide range of habitat- related concepts, with different uses and understandings of the word ‘habitat’ itself has arisen as a consequence. Inconsistencies in terminology can cause confusion between studies, making it difficult to investigate and understand the ecology of fish and the factors that affect their survival. Ultimately, the inability to discern the relationships between fish and their environment clearly can hinder conservation and management measures for fish populations. This review identifies and addresses the present ambiguity surrounding definitions of habitat and habitat related concepts currently used in spatial management of demersal marine fish populations. The role of spatial and temporal scales is considered, in addition to examples of how to assess fish habitat for conservation and management purposes.
... Although not as devastating as dredging, European maerl beds have also been impacted by aquaculture (Hall-Spencer et al. 2006 ;Hall-Spencer and Bamber 2007 ;Peña and Bárbara 2008a ;Peña 2010 ), changes in current patterns associated with construction (Birkett et al. 1998a ;Grall and Hall-Spencer 2003 ), dredge fi sheries (Hall-Spencer 1998 ;Hall-Spencer and Moore 2000 ;Hall-Spencer et al. 2003 ;Hauton et al. 2003 ;Kamenos et al. 2003 ), as well as increased sedimentation and eutrophication (Hily et al. 1992 ;Grall and Glemarec 1997 ). There is also a growing realisation that these habitats may be especially vulnerable to ocean acidifi cation since the high Mg-calcite skeletons of coralline algae dissolve easily as CO 2 levels rise (Nelson 2009 ;Büdenbender et al. 2011 ;Porzio et al. 2011 ;Diaz-Pulido et al. 2012 ;Noisette et al. 2013 , see Chapter by Martin and Hall-Spencer). ...
Chapter
Beds of coralline algal sediment form ecologically and economically important habitats in the North Atlantic. These habitats can occur from the intertidal down to 60 m depth, and they are locally abundant in several countries. Thirteen species of coralline algae form rhodoliths or maerl in this region; Lithothamnion corallioides, L. glaciale, L. tophiforme and Phymatolithon calcareum are the most widely recorded. The structure and biodiversity of these habitats is destroyed by dredging and can be degraded by towed demersal fishing gear and by mussel and salmon farming. Legislation has been passed in the European Union (EU) to protect P. calcareum and L. corallioides which should be extended to include the other maerl species from the region. Outside the EU there is a lack of baseline information concerning the importance of these habitats: a fuller understanding of their role may lead to protection in Scandinavia, Iceland and the Atlantic coasts of Canada and the United States. The design of such protected areas would need to consider the ongoing effects of invasive species, ocean warming and acidification.
... M. merlangus were also observed in higher relative abundance with increasing substratum extent. The increase in G. morhua observed with increasing landscape heterogeneity may enable G. morhua to access areas with possibly increased food availability and areas with sufficient refuge [8,67,68]. An experimental study undertaken by [69] demonstrated that juvenile G. morhua seem to differentiate between substratum types, selecting areas where growth and survival were highest. ...
Article
Full-text available
Nature conservation and fisheries management often focus on particular seabed features that are considered vulnerable or important to commercial species. As a result, individual seabed types are protected in isolation, without any understanding of what effect the mixture of seabed types within the landscape has on ecosystem functions. Here we undertook predictive seabed modelling within a coastal marine protected area using observations from underwater stereo-video camera deployments and environmental information (depth, wave fetch, maximum tidal speeds, distance from coast and underlying geology). The effect of the predicted substratum type, extent and heterogeneity or the diversity of substrata, within a radius of 1500 m around each camera deployment of juvenile gadoid relative abundance was analysed. The predicted substratum model performed well with wave fetch and depth being the most influential predictor variables. Gadus morhua (Atlantic cod) were associated with relatively more rugose substrata (Algal-gravel-pebble and seagrass) and heterogeneous landscapes, than Melanogrammus aeglefinus (haddock) or Merlangius merlangus (whiting) (sand and mud). An increase in M. merlangus relative abundance was observed with increasing substratum extent. These results reveal that landscape effects should be considered when protecting the seabed for fish and not just individual seabed types. The landscape approach used in this study therefore has important implications for marine protected area, fisheries management and monitoring advice concerning demersal fish populations.
... Equally, maerl was not treated separately from gravel-pebble substratum type because of its gravel-pebble sized form around south of Arran. In addition impacted maerl has been demonstrated to be more similar to gravel than live maerl (Kamenos et al. 2003). As a result of insufficient prior knowledge of the substratum types of the area, the experimental design was unbalanced. ...
Article
Full-text available
Stereo-video scuba transects were conducted during daylight hours from June to September 2013 within a proposed marine protected area (MPA) in the Firth of Clyde, west of Scotland. More juvenile Atlantic cod Gadus morhua of fork length (LF ) range 6-11 cm were observed in substrata containing mixed gravel, including maerl, than in boulder-cobble substrata with high algal cover, or sand with low density seagrass. Community composition was significantly different between substratum types. A decrease in G. morhua abundance was observed over the period of data collection. Over time, mean and variance in G. morhua LF increased, indicating multiple recruitment events. Protecting mixed gravel substrata could be a beneficial management measure to support the survival and recruitment of juvenile G. morhua; other substrata might be important at night given their diel migratory behaviour. Stereo-video cameras provide a useful non-destructive fisheries-independent method to monitor species abundance and length measurements.
Article
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Report to the Countryside Council for Wales, English Nature, Scottish Natural Heritage and the Joint Nature Conservation Committee. March 2005 Reference: Sewell, J. & Hiscock, K., 2005. Effects of fishing within UK European Marine Sites: guidance for nature conservation agencies. Report to the Countryside Council for Wales, English Nature and Scottish Natural Heritage from the Marine Biological Association. Plymouth: Marine Biological Association. CCW Contract FC 73-03-214A. 195 pp.
Article
Full-text available
The ongoing increase in anthropogenic carbon dioxide (CO2) emissions is changing the global marine environment and is causing warming and acidification of the oceans. Reduction of CO2 to a sustainable level is required to avoid further marine change. Many studies investigate the potential of marine carbon sinks (e.g. seagrass) to mitigate anthropogenic emissions, however, information on storage by coralline algae and the beds they create is scant. Calcifying photosynthetic organisms, including coralline algae, can act as a CO2 sink via photosynthesis and CaCO3 dissolution and act as a CO2 source during respiration and CaCO3 production on short-term time scales. Long-term carbon storage potential might come from the accumulation of coralline algae deposits over geological time scales. Here, the carbon storage potential of coralline algae is assessed using meta-analysis of their global organic and inorganic carbon production and the processes involved in this metabolism. Organic and inorganic production were estimated at 330 g C m−2 yr−1 and 880 g CaCO3 m−2 yr−1 respectively giving global organic/inorganic C production of 0.7/1.8 × 109 t C yr−1. Calcium carbonate production by free-living/crustose coralline algae (CCA) corresponded to a sediment accretion of 70/450 mm kyr−1. Using this potential carbon storage by coralline algae, the global production of free-living algae/CCA was 0.4/1.2 × 109 t C yr−1 suggesting a total potential carbon sink of 1.6 × 109 t C yr−1. Coralline algae therefore have production rates similar to mangroves, saltmarshes and seagrasses representing an as yet unquantified but significant carbon store, however, further empirical investigations are needed to determine the dynamics and stability of that store.
Article
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Maerl beds are formed by the accumulation of free-living coralline algae and have considerable ecological significance due to the high diversity of associated fauna and flora. The rapid expansion of the Atlantic salmon Salmo salar aquaculture industry in Norway may have major impacts on surrounding maerl beds through the release of effluents, including fish faeces. This study is the first to test the effects of salmon faeces and inorganic sediment deposition on the photosynthesis, respiration, calcification and pigment content of the coralline alga Lithothamnion soriferum . In a 6 wk laboratory experiment, inorganic sediment and salmon faeces deposition significantly reduced the amount of light reaching the surface of coralline algae. No impact of inorganic sediment deposition was detected on L. soriferum physiology, while salmon faeces deposition increased respiration rate and reduced net primary production and calcification. The accumulation of salmon faeces stimulates proliferation of bacteria, with adverse consequences on L. soriferum physiology due to the potential release of toxic compounds. Burial by salmon faeces deposition also affects the physiology of coralline algae due to the flocculation of sticky faeces particles, which may limit nutrient and gas exchanges in the vicinity of thalli. Carbon dioxide accumulation in the vicinity of L. soriferum may lead to a decline in pH and alter the calcification process in cell walls. In natural maerl beds, the negative effect of faeces deposition may be exacerbated by longer-term exposure and the presence of other chemicals released by fish farms.
Article
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Rhodolith beds are the dominant submerged calcifying aquatic vegetation in some coastal marine environments worldwide but few quantitative data are available regarding their physiology. In the Gulf of California (Mexico), Lithophyllum margaritae (Rhodophyta, Corallinaceae) is the most abundant nongeniculate, rhodolith-forming coralline species. Over their gulf-wide distribution, rhodoliths are exposed to a wide range of seasonal temperatures (~8-32ºC). The effect of changes in temperature on the photosynthetic and calcification rates of this species is unknown. We therefore evaluated the effect of temperature (10-30ºC) on the photosynthetic and calcification rates of L. margaritae rhodoliths in the lab and examined the effect of seasonal changes in temperature on growth rates in the field. Photosynthetic rates were evaluated polarographically and calcification rates were evaluated in the lab using both the buoyant weight technique and total alkalinity method, and in the field through alizarin staining. To the best of our knowledge, this is the first time that these three methods are used simultaneously to evaluate growth rates in coralline algae. Photosynthetic, calcification and growth rates showed wide fluctuations as a result of laboratory or field temperature. Photosynthetic (Pmax) and respiratory rates both increased five-fold as incubation temperature increased to 25- 30ºC. Similarly, calcification rates in the lab and growth rates in the field increased with higher temperatures. The lab data suggest that rhodolith growth is seasonally regulated by seawater temperature. The buoyant weight and total alkalinity techniques for determining calcification rate were comparable at low temperatures, but variability increased with temperature and this will be examined in further studies. Field growth rates, presented as apical tip extension, were significantly higher in summer (5.02 ± 1.16 mm yr-1) than in winter (0.83 ± 0.16 mm yr-1), supporting the lab results. The strong effects of temperature on photosynthetic, calcification and growth rates of Lithophyllum margaritae in the Gulf of California suggest that changes in sea surface temperature directly regulate bed production
Article
Beds of nongeniculate coralline algae, known as rhodolith beds or maerl, occur throughout the world. They are protected under European legislation due to their high conservation value; however, within Europe there are significant areas of dead maerl deposits and the causes of the demise of these past habitats is not always clear. In this study we utilize radiocarbon dating techniques to constrain the time of the maerl bed deaths from a number of historical or pre-historical possibilities. We highlight the threat from burial to these precious habitats, which has implications for contemporary conservation. We found that a maerl bed in Strangford Lough, Northern Ireland, was killed around 4200 14C BP (before present, AD 1950), which is the same as a previously reported maerl bed death in Marseille, France. This also coincides with evidence of a significant period of climatic change. The case study of Belfast Lough highlights the modern threat to maerl bed by sedimentation caused by channel dredging, which complements previous experimental work.
Article
The biodiversity of the oceans is a hot topic, as witnessed by the announcements I received for three international symposia/workshops on marine biodiversity in the fall of 1998. It is also a broad topic encompassing the description of global diversity patterns, molecular studies of gene flow on single shores, and application of “integrated coastal zone management” to species preservation in multiple-use ecosystems. A book capturing the timeliness and breadth of this topic, while highlighting research needs and conservation concerns, would indeed be useful for enlightening the public, educating students, and focusing researchers in this important, if amorphous, field. Marine Biodiversity: Pattern and Process is designed to fill this niche. The premise of the volume, as eloquently argued by Sir Crispin Tickell, is that marine ecosystems are suffering the onslaught of humanity at a time when we have but a glimmering of the extent and vulnerability of their biodiversity. The editors thus bring together key studies evaluating the patterns and processes underlying biodiversity in coastal zones to the abyss, from equatorial waters to polar seas.
Article
Maerl beds are mixed sediments built by a surface layer of slow-growing, unattached coralline algae that are of international conservation significance because they create areas of high biodiversity. They are patchily distributed throughout Europe (to 30 m depth around the British Isles and to 120 m depth in the Mediterranean) and many are affected by towed demersal fishing. We report the effects of Newhaven scallop dredges on a previously unfished maerl bed compared with the effects on similar grounds that have been fished commercially in the Clyde Sea area, Scotland. Sediment cores were taken to assess the population density of live maerl thalli prior to scallop dredging on marked test and control plots. These plots were then monitored biannually over a four-year period. Live maerl thalli were sparsely distributed at the impacted site, and experimental dredging had no discernible effect on their numbers. The previously unfished ground had dense populations of live maerl and scallops (both Aequipecten opercularis and Pecten maximus). While counts of live maerl remained high on the control plot, scallop dredging led to a >70% reduction with no sign of recovery over the subsequent four years. The vulnerability of maerl and associated benthos (e.g., the delicate bivalve, Limaria hians) is discussed in relation to towed demersal fishing practices. 2000 International Council for the Exploration of the Sea Key words: benthos, ecosystem effects, long-term impact, maerl beds, scallop dredging.
Article
Maerl beds are little studied shallow marine habitats that have a patchy distribution around the British Isles. They are mixed sediment deposits built by a surface layer of slow growing coralline seaweeds that are of international conservation significance. Baseline information is provided on the high diversity and abundance of mollusc assemblages associated with Scottish maerl deposits. Commercial extraction and the use of towed demersal fishing gears kills the plants upon which survival of this habitat depends. The molluscan fauna of a site impacted by scallop dredging is compared with that of an unimpacted site. The need to conserve maerl habitats is highlighted as there is concern over the extent to which maerl beds are being disturbed in Europe and how activities such as scallop dredging affect the ecology of these fragile nearshore habitats.
Article
Five sedimentary facies are described from SCUBA diving examination and sampling of Mannin Bay, Ireland. A Bank facies is built up by the unattached coralline algae Lithothamnium corallioides and Phymatolithon calcareum. This autochthonous facies occurs in shallow sheltered environments. In exposed areas a rippled Clean Algal Gravel facies is found composed of coralline and molluscan debris. In intermediate energy areas a Muddy Algal Gravel facies is found with small amounts of live corallines. Sheltered creeks have a Mud facies which is partly carbonate and partly terrigenous. The shallow water coralline algal sediments are overlapped by a Fine Sand facies of mixed biogenic composition. Each facies is characterized by particular phenotypic growth forms of the unattached corallines. Rates of organic calcium carbonate production are obtained which are found to be similar to rates from shallow tropical non-reef environments. The carbonate sediments of Mannin Bay are compared with similar sediments from Kilkerrin Bay. Ireland, from Brittany and from Falmouth Harbour. From these comparisons, facies models are proposed for these carbonate sediments. The major factor controlling facies distribution is coastal morphology. The present day shelf is considered to be too exposed to preserve complete sequences of the shallow water sediments.
E¡ects of ¢shing on nontarget species and habitats: biological, conservation and socio-economical issues
  • M J Kaiser
  • S J Groot
  • De
Kaiser, M.J. & Groot, S.J. de, ed., 2000. E¡ects of ¢shing on nontarget species and habitats: biological, conservation and socio-economical issues. Oxford: Blackwell Science.
Is bottom trawling partly responsible for the regression of Posidonia oceanica meadows in the Mediterrranean Sea? In E¡ects of ¢shing on non-target species and habitats: biological, conservation and socio-economic issues
  • G D Ardizzone
  • P Tucci
  • A Somaschini
  • A Belluscio
Ardizzone, G.D., Tucci, P., Somaschini, A. & Belluscio, A., 2000. Is bottom trawling partly responsible for the regression of Posidonia oceanica meadows in the Mediterrranean Sea? In E¡ects of ¢shing on non-target species and habitats: biological, conservation and socio-economic issues (ed. M.J. Kaiser and S.J. de Groot), pp. 37^46. Oxford: Blackwell Science. BIOMAERL team, 1999. Final Report (in 2 vols.), BIOMAERL Project (Co-ordinator: P.G. Moore, University Marine Biological Station Millport, Scotland), EC Contract No. MAS3-CT95-0020. Pp. 1^541, 542^973 þ Appendix.
Is bottom trawling partly responsible for the regression of Posidonia oceanica meadows in the Mediterrranean Sea?
  • G D Ardizzone
  • P Tucci
  • A Somaschini
  • A Belluscio
Ardizzone, G.D., Tucci, P., Somaschini, A. & Belluscio, A., 2000. Is bottom trawling partly responsible for the regression of Posidonia oceanica meadows in the Mediterrranean Sea? In E¡ects of ¢shing on non-target species and habitats: biological, conservation and socio-economic issues (ed. M.J. Kaiser and S.J. de Groot), pp. 37^46. Oxford: Blackwell Science. BIOMAERL team, 1999. Final Report (in 2 vols.), BIOMAERL Project (Co-ordinator: P.G. Moore, University Marine Biological Station Millport, Scotland), EC Contract No. MAS3-CT95-0020. Pp. 1^541, 542^973 þ Appendix.