Content uploaded by Barbro Taraldset Haugland
Author content
All content in this area was uploaded by Barbro Taraldset Haugland on Mar 25, 2021
Content may be subject to copyright.
A preview of the PDF is not available
Large-scale salmon farming in Norway impacts the epiphytic community of Laminaria hyperborea
Abstract
Large-scale finfish farms are increasingly located in dispersive hard-bottom environments where Laminaria hyperborea forests dominate; however, the interactions between farm effluents and kelp forests are poorly understood. Effects of 2 levels of salmonid fish-farming effluents (high and low) on L. hyperborea epiphytic communities were studied by sampling canopy plants from 12 sites in 2 high-energy dispersive environments. Specifically, we assessed if farm effluents stimulated fast-growing epiphytic algae and faunal species on L. hyperborea stipes—as this can impact the kelp forest community composition—and/or an increased lamina epiphytic growth, which could negatively impact the kelp itself. We found that bryozoan biomass on the stipes was significantly higher at high-effluent farm sites compared to low-effluent farm and reference sites, resulting in a significantly different epiphytic community. Macroalgal biomass also increased with increasing effluent levels, including opportunistic Ectocarpus spp., resulting in a less heterogeneous macroalgae community at high-effluent farm sites. This habitat heterogeneity was further reduced by the high bryozoan biomass at the high-effluent sites. Such changes in the epiphyte community could have implications for the faunal community that relies on the epiphytes for food and refuge. On the kelp lamina, no clear response to farm effluents was found.
Supplementary resource (1)
... In Norway, the most common epigrowth on kelp lamina are usually filamentous seaweeds and bryozoans such as Electra pilosa and Membranipora membranacea (Haugland et al. 2021), but both colonial and solitary ascidians have also been observed on kelp. Bryozoan biofouling can lead to weakening, breakage, and detachment of the lamina (Krumhansl et al. 2011). ...
This is an assessment of risk and risk-reducing measures related to the introduction and dispersal of the invasive alien carpet tunicate Didemnum vexillum in Norway.
... Nutrient enrichment generally favours ephemeral species over perennial algal species because of their more efficient nutrient uptake and faster growth (Karez et al., 2004;Wallentinus, 1984). Dissolved nutrients as effluents from fish farms were already found to increase cover of epiphytic or opportunistic species for example in the Baltic Sea (Rönnberg et al., 1992;Worm and Sommer, 2000), the Tasman Sea (Fowles et al., 2018a(Fowles et al., , 2018bOh et al., 2015), and Norwegian fjords (Haugland et al., 2021). Thereby, macroalgal species assemblages changed towards more green, fast-growing or filamentous algal species near fish farms (Boyra et al., 2004;Fowles et al., 2018a;Rönnberg et al., 1992). ...
Eutrophication is a major threat to aquatic ecosystems, because excessive nutrient enrichment may result in the loss of ecosystem services. Fjord systems are specifically under pressure due to nutrient input from land (agriculture) and sea (aquaculture). In this bioassay study, we have analyzed the effect of different nutrient sources, as well as their combination, on growth, nutrient composition and recruitment of habitat-forming and ephemeral macrophytes. We found that agricultural fertilizer increased growth for all algae (except Fucus), while the fish farm effluents mainly increased growth of Ulva. The C:N ratio was hardly affected by the fish farm, but decreased significantly in all algae when agriculture fertilizer was added. Most interestingly, however, distance to the fish farm modulated the algal response to the fertilizer. Our results demonstrate the importance of studying effects of multiple stressors in aquatic ecosystems to sustainably manage the consequences of anthropogenic impacts.
... Differently sourced seaweeds may also generate different responses to biotic and abiotic stresses; for example, the Phaeophyceae Silvetia compressa from northern California responded to low levels of herbivore grazing whereas S. compressa from southern California did not, even after 24 days of acclimatization [20]. Epiphyte presence and abundance is another consideration, both for the health and yield of the cultivated seaweed which could be negatively affected [21]; and for contamination in subsequent processing. ...
Using brown seaweed kelp species Saccharina latissima and Laminaria digitata as feedstocks, a set of pilot-scale macroalgae processing batches were conducted (50–200 kg per batch) for the production of a range of food-grade liquid and solid fractions. The aim of this communication is to relay a number of lessons learnt during this period in combination with previous relevant observations and considerations for others who are intending to process macroalgae at scale. The novelty of this paper is thus to form a bridge between academic findings and practical know-how. Considerations covers material diversity; abiotic and biotic impact and variation; and supply chain considerations. Observations covers milling and cutting; equipment requirements; and acids including their effects on heavy metals, especially lead. Recommendations summarises key points from this pilot-scale and previous work. These include: harvest seasonality, water quality and proximity to processing facilities; minimising contaminants within the macroalgae such as stones and shells; considering equipment composition and volume for all steps and processes including final product quality; acid choice and its effects on both the equipment used and the metals bioaccumulated within the macroalgae.
Norway has complicated dynamics in the coastal ocean and in the fjords. In this area is also the largest salmon aquaculture industry in the world. The salmon industry is valuable for Norwegian economy worth more than 60 billion NOK. Thus, it is important to know the physical oceanography along the coast, even variability on short temporal and spatial scales (h/km), to be able to quantify environmental effects of the aquaculture industry. This is the motivation behind the implementation of a current model covering the whole coast of Norway with a relatively high spatial grid size of 800 m. The NorKyst800 is an implementation of the ROMS current model with an elaborated system of forcing and boundary conditions. This model has an important role for Norwegian authorities in various management purposes. We show that the NorKyst800 results are realistic and typically deviating at most by 1 °C and one unit in salinity from observations. The currents in the upper 10–20 m of the water column vary in a similar way as observed current and the agreement is good. The usefulness of a tool like the NorKyst800 is illustrated by an example of dispersion of salmon lice which is the biggest problem the salmon industry presently is facing. Detailed information, as can be provided by NorKyst800, is needed to fully understand and quantify environmental effects of the aquaculture industry. Similar modeling systems describing the planktonic salmon lice concentration operationally could be beneficial also in other salmon-producing countries like Scotland, Canada, or Chile. The major requirement will be access to updated number of fish and female lice per fish on a weekly time scale.
The influence of substrate type and particle age on the remobilization of settled Atlantic salmon Salmo salar faecal material was studied through a set of controlled experiments in horizontal flow flumes, simulating different bottom conditions present in fish-farming locations along the coast of Norway. There was no significant effect of pellet age on remobilization for up to 1 week old faecal material, but critical shear stresses (τ c ) and velocities required for resuspending faecal pellets were strongly dependent on substrate type. Smooth substrates such as mud and rock slate required lower stresses for the onset of faeces resuspension (τ c %%CONV_ERR%% 0.06 Pa) than rougher surfaces such as sand (τ c %%CONV_ERR%% 0.12 Pa) or fragmented rock (τ c %%CONV_ERR%% 0.32 Pa), where bedforms and large fractures shield the particles from the direct influence of the drag forces. These newly determined substrate-dependent τ c resuspension thresholds will contribute to the construction of more accurate numerical models that include bottom type as a parameter regulating the extent of particle spreading, in contrast to the constant-value approach that has been used to date.
The production and fate of seaweed detritus is a major unknown in the global C-budget. Knowing the quantity of detritus produced, the form it takes (size) and its timing of delivery are key to understanding its role as a resource subsidy to secondary production and/or its potential contribution to C-sequestration. We quantified the production and release of detritus from 10 Laminaria hyperborea sites in northern Norway (69.6° N). Kelp biomass averaged 770 ± 100 g C m−2 while net production reached 499 ± 50 g C m−2 year−1, with most taking place in spring when new blades were formed. Production of biomass was balanced by a similar formation of detritus (478 ± 41 g C m−2 year−1), and both were unrelated to wave exposure when compared across sites. Distal blade erosion accounted for 23% of the total detritus production and was highest during autumn and winter, while dislodgment of whole individuals and/or whole blades corresponded to 24% of the detritus production. Detachment of old blades constituted the largest source of kelp detritus, accounting for > 50% of the total detrital production. Almost 80% of the detritus from L. hyperborea was thus in the form of whole plants or blades and > 60% of that was delivered as a large pulse within 1–2 months in spring. The discrete nature of the delivery suggests that the detritus cannot be retained and consumed locally and that some is exported to adjacent deep areas where it may subsidize secondary production or become buried into deep marine sediments as blue carbon.
The processes limiting the population recovery of the kelp Saccharina latissima after recent large‐scale loss from the south coast of Norway are poorly understood. Previous investigations do, however, suggest that the impacts of biotic interactions (epibiosis and competition) and increased water turbidity are important. We investigated the depth‐related patterns of growth, epibiosis, and mortality in two sample populations of kelp, from the south and the southwest coast of Norway. The investigations were performed over a period of seven months, in a crossed translocational study, where kelps were mounted on rigs at six depths (1, 3, 6, 9, 15, and 24 m). In a second experiment, the amounts of light blocked by different epibiont layers growing on the kelp frond were investigated. While growth decreased with depth in spring and summer, the kelp grew faster at 15 m than at shallower depths in fall. Survival was low both in shallow water and below 15 m depth. Epibionts covered the kelp growing at depths from 1 to 9 m, and the laboratory study showed that the coverage may have deprived the individuals of as much as 90% of the available light. Although the depth‐related results we present apply—in the strictest sense—only to kelp translocated on rigs, we argue that the relative patterns are relevant for natural populations. Growth and survival of S. latissima is likely to be reduced by heavy loads of epibionts, while depths where epibionts are sparse may be close to the lower limit of the kelps depth distribution along the south coast of Norway. This suggests that a vertical squeeze, or narrowing of the distribution range of kelp forests may be occurring in Norway.
Global expansion of salmon aquaculture is contingent upon finding new, large-capacity farming locations that are, increasingly, situated in dispersive environments with atypical ecological characteristics. The capacity of such sites to assimilate organic waste and the type and spatial extent of effects remain poorly understood. This study couples intensive spatial and temporal measurements of waste outputs with measurements of benthic ecological diversity and sediment biogeochemistry at a shallow dispersive site on the central west coast of Norway. Despite minimal visual changes to the seabed, pronounced biological effects were evident out to 600-1000 m away from the farm. Greatly enhanced faunal and microbial activity was tightly coupled with strong sediment respiratory responses in the form of oxygen uptake and ammonia efflux. The benthic response was highly dynamic, with rapid and prolific colonization by opportunistic fauna, followed by substantive recovery during the subsequent 7 mo fallowing period. The fate and pathways of farm waste through the environment was compartmentalized by converting measured parameters into equivalent carbon fluxes. During early production, approximately 30-40% of the waste was accounted for by the measured benthic processes, attributed to faunal respiratory activity and the physical properties including sediment type. Later in the production cycle, a sediment burial event was observed down-current from the farm. The remaining 60-70% of organic waste was assumed to be either assimilated in the water column, consumed by large, unquantified benthic fauna, or exported and dispersed. Shallow, dispersive sites therefore appear relatively resilient to acute near-field enrichment, but are also more likely to result in accumulative, far-field effects.
Sammendrag (norsk):
Havforskningsinstituttet gjennomførte i april 2018 videoundersøkelser på C-felt for stortarehøsting i Sør-Trøndelag og Nord-Trøndelag, et snaut halvår før disse feltene, etter gjeldende forvaltningsplaner, åpnes for tarehøsting 1. oktober 2018. Tilsvarende undersøkelser ble også gjennomført på referansestasjoner i områder der tarehøsting ikke er tillatt. På bakgrunn av tarevegetasjonens tilstand og tetthet av kråkeboller gjøres en vurdering av hvert enkelt felts egnethet for tarehøsting kommende sesong.
I Sør-Trøndelag varierte tilstanden mellom ulike områder, og på enkelte høstefelt ved Hitra (4C, 9C, 14C, 68C), Frøya (58C, 63C), i Ørland (73C) og Bjugn (78C, 83C) ble det observert reduserte forekomster av stortare og/eller høy tetthet av rød kråkebolle (Echinus esculentus). Tarehøsting frarådes derfor på disse feltene i 2018/2019. Tarehøsting frarådes også i østlige deler av felt 29C ved Frøya før 1. mai 2019, pga. at deler av stortarevegetasjonen er lite utviklet i dette området.
I Nord-Trøndelag tyder observasjonene på god tilstand i taresamfunnene med en gjennomsnittlig dekningsgrad av stortare på ca. 90 % og lav tetthet av kråkeboller. På høstefeltene 18C og 33C er deler av stortarevegetasjonen fortsatt i en utviklingsfase og tarehøsting frarådes her før 1. mai 2019. På grunn av lav biomassetetthet av stortare frarådes tarehøsting på felt 58C i 2018/2019 og på felt 13C før 1. mai 2019.
Summary (English):
The Institute of Marine Research monitored kelp (Laminaria hyperborea) communities in Sør-Trøndelag and Nord-Trøndelag counties in April 2018. The monitoring was performed along video transects at kelp harvesting fields classified into category C, targeting for harvesting in the period 1 October 2018 – 30 September 2019, as well as in control areas were kelp harvesting is prohibited.
In Sør-Trøndelag the condition of the kelp-vegetation varied between regions. On C-fields at Hitra (4C, 9C, 14C, 68C), Frøya (58C, 63C), Ørland (73C) and Bjugn (78C, 83C) municipalities, the kelp vegetation was not considered suitable for harvesting in 2018–2019, mainly due to limited stocks of kelp (L. hyperborea) and presence of sea urchins (Echinus esculentus). On one field (29C) west of Frøya island, parts of the kelp vegetation were still in an early developmental phase and harvesting in the eastern section of this field is not advisable before 1 May 2019.
On most C-fields in Nord-Trøndelag the kelp vegetation appeared in a healthy state, with high coverage of L. hyperborea and few sea urchins. However, the size and development of the kelp vegetation appeared limited in some fields, most notably 58C where kelp harvesting is not advisable in 2018–2019, as well as 13C, 18C and 33C where kelp harvesting is not advisable before 1 May 2019.
The aim of this study was to define the waste plume dynamics around a salmon farm in Norway. Systematic water sampling and numerical modeling were implemented to define nutrient concentrations in the upper water column at long-term (seasonal) and short-term (between and within days) time scales. Nutrient enhancement was observed for ammonium only, while the concentrations of orthophosphate and organic wastes were never higher than the background values. The spatial magnitude of cage effluent dispersion was limited. Empirical results detected enhanced concentrations up to 100 m down-current of the farm when fish biomass was high. Model results showed that the zone of influence could occasionally reach to >1000 m. In the first year of production, when fish biomass was low, no enhancement was detected, and in April and September of the following year, average ammonium concentrations were respectively 0.2 and 0.8 µM above the background concentrations. Taking the ambient seasonal variability into account, this resulted in 1.6 times higher concentrations for both sampling months. The measured short-term temporal variability in nutrient concentrations near the cages varied up to 2 times from day to day and were 3.5 times higher in the evening compared to the morning. As seasonal investigations were performed in the morning, maximum enhancement was likely underestimated. The rapid decrease in nutrient concentrations with increasing distance from the cages suggests that the farm studied here is currently not causing significant degradation of surface water quality. Results of this study contribute to evaluating the potential for ecological mitigation of waste nutrients and provide directions for design of optimized integrated multi-trophic aquaculture facilities
Environmental management of coastal aquaculture is focused on acute impacts of organic and nitrogenous wastes close to farms. However, the energy-rich trophic subsidy that aquaculture provides may create cascades with influences over broader spatial scales. In a fjord region with intensive fish farming, we tested whether an ecosystem engineer, the white urchin Gracilechinus acutus, was more abundant at aquaculture sites than control sites. Further, we tested whether diets influenced by aquaculture waste altered reproductive outputs compared with natural diets. Urchins formed barrens at aquaculture sites where they were 10 times more abundant (38 urchins m⁻²) than at control sites (4 urchins m⁻²). Urchins were on average 15 mm larger at control sites. In the laboratory, urchins fed aquafeed diets had 3 times larger gonad indices than urchins fed a natural diet. However, their reproduction was compromised. Eggs from females fed an aquafeed diet had 13% lower fertilisation success and 30% lower larval survival rates at 10 d compared with females fed a natural diet. A reproductive output model showed that enhanced numbers of 10 d old larvae produced by the dense aquaculture-associated aggregations of G. acutus will supersede any detrimental effects on reproduction, with larval outputs from aquaculture sites being on average 5 times greater than control sites. The results show that aquaculture waste can act as a trophic subsidy in fjord ecosystems, stimulating aggregations of urchins and promoting the formation of urchin barrens. Where finfish aquaculture is concentrated, combined effects on the wider environment may produce ecosystem-level consequences.
Kelp forests are structurally complex habitats, which provide valuable services along 25% of the world's coastlines. Globally, many kelp forests have disappeared and been replaced by turf algae over the last decade. Evidence that environmental conditions are becoming less favorable for kelps, combined with a lack of observed recovery, raises concern that these changes represent persistent regime shifts. Here, we show that human activities mediate turf transitions through geographically disparate abiotic (warming and eutrophication) and biotic (herbivory and epiphytism) drivers of kelp loss. Evidence suggests kelp forests are pushed beyond tipping points where new, stabilizing feedback systems (sedimentation, competition, and Allee effects) reinforce turf dominance. Although these new locks on the degraded ecosystems are strong, a mechanistic understanding of feedback systems and interactions between global and local drivers of kelp loss will expose which processes are easier to control. This should provide management solutions to curb the pervasive trend of the flattening of kelp forests globally.
Norwegian::
Havforskningsinstituttet gjennomførte i april-juni 2017 videoundersøkelser på B-felt for tarehøsting i Møre
og Romsdal, et snaut halvår før disse feltene, etter gjeldende forvaltningsplaner, åpnes for tarehøsting 1.
oktober 2017. Tilsvarende undersøkelser ble også gjennomført på referansestasjoner i områder der
tarehøsting ikke er tillatt. På bakgrunn av stortarevegetasjonens tilstand og kråkebolletetthet gjøres en
vurdering av hvert enkelt felts egnethet for tarehøsting kommende sesong.
Observasjonene tyder på at tilstanden på de fleste B-felt er god med en gjennomsnittlig dekningsgrad av
stortare på ca. 75 % og lav tetthet av kråkeboller. I sørlige deler av fylket var gjennomsnittshøyden av
stortarevegetasjonen på høstefeltene noe lavere enn i referanseområdene, mens det var mindre forskjeller
i nordlige deler. På enkelte stasjoner var stortarevegetasjonen mindre utviklet, med lavere forekomster og
kortvokste planter. Dette gjelder spesielt høstefeltene 12B og 5B i Sandøy kommune, der tarehøsting
frarådes før 1. mai 2018. På øvrige B-felt i Møre og Romsdal vurderes stortarevegetasjonens tilstand som
tilstrekkelig god til at høsting kan igangsettes fra og med 1. oktober 2017.
English:
The Institute of Marine Research monitored kelp (Laminaria hyperborea) communities on kelp-harvesting
fields in Møre og Romsdal in April-June 2017. The monitoring was performed by underwater video, along
transects in fields classified into category B, targeted for kelp-harvesting in the period 1 October 2017 – 30
September 2018, as well as in reference areas where harvesting is prohibited.
Although the canopy sizes of the kelp vegetation on the previously harvested B-fields appeared to be of a
slightly smaller size than in the reference areas, the state of the kelp vegetation was considered healthy on
most B-fields, with high coverage of Laminaria hyperborea and few sea urchins. However, the abundance
and development of the kelp vegetation appeared limited on some fields, most notably 12B and 5B in
Sandøy, and kelp harvesting on those fields is not advisable before 1 May 2018. The condition of the kelp
vegetation on the remaining B-fields in Møre og Romsdal appeared in a better state, and those fields may
be considered for harvesting from 1 October 2017.