Mussel Growth Research Articles

Mussel farming production capacity and food web interactions in a mesotrophic environment

Low trophic aquaculture (LTA), such as bivalve farming, offers promising avenues to supply sustainable seafood and aquafeed. While bivalve farming usually occurs in highly productive coastal areas which already support numerous human activities and suffer from environmental pressures, numerical tools offer a promising avenue to explore and assess biomass production potential and associated ecosystemic impacts for further development of the industry and prospection of new exploitation sites. In this study, we coupled an ecophysiological model, the dynamic energy budget theory (DEB), with an ecosystem model (NORWECOM.E2E) to simulate blue mussel Mytilus spp. farming production and effects based on the food web in the mesotrophic Hardangerfjord in western Norway. We tested several levels of fjord-scale farming intensity and assessed 2 production purposes: aquafeed and human consumption. Results suggested the Hardangerfjord could host large-scale mussel farming for both purposes. However, large exploitation schemes displayed detrimental effects on individual mussel growth (39% less wet mass after 2 yr) and especially on secondary production (decrease of 33% after 1 yr) due to acute trophic competition. Simulations showed short production cycles for aquafeed were more efficient to exploit primary production, since young and small mussels have lower maintenance and reproduction costs. Dissolved nutrient inputs from salmonid farms had marginal effects on primary production (<2%). However, salmonid and mussel farming activities could compete for the sites with the highest production potential.

Effects of seasonal changes and depth on growth parameters of the Mediterranean mussel (Mytilus galloprovincialis) on a shipwreck in the Eastern Mediterranean Sea

AbstractThe study was conducted between July 2018 and May 2020 to compare seasonal changes in growth parameters of the Mediterranean mussel (Mytilus galloprovincialis) at different depths in two different areas of the Northeastern Mediterranean Sea (Aegean Sea). In a preliminary study, mussels were placed in cages at different depths of an artificial reef (AR – shipwreck) and natural reef (NR). Temperature, salinity, pH, and dissolved oxygen were determined seasonally at both sites at a depth of 37 m (deepwater) and 25 m (midwater). Linear increases in length and width of mussels at the AR site were recorded, while no consistent changes were observed for mussels at the NR. There was negative correlation between the specific growth rate (SGR) and salinity (r2= 0.5098) and temperature (r2= 0.1470) at the AR site. Negative correlations were also recorded between pH and the commercial condition index (CCI) at both the AR (r2= 0.3869) and NR (r2= 0.3600) sites. Our findings show that depth had a significant effect (p< 0.05) on theCCIof mussels at the NR site, while its effect was insignificant for this index at the AR site (p> 0.05). This study indicates that natural reefs provide more suitable conditions for the growth of Mediterranean mussels than shipwrecks used as artificial reefs.

Ocean acidification alters anti-predator responses in a competitive dominant intertidal mussel

Widespread intertidal mussels are exposed to a variety of natural and anthropogenic stressors. Even so, our understanding of the combined influence of stressors such as predation risk and ocean acidification (OA) on these species remains limited. This study examined the response of the purple mussel (Perumytilus purpuratus), a species distributed along Pacific southeastern rocky shores, to the effects of predation risk and OA. Using a laboratory 2 × 2 cross design, purple mussels were either devoid or exposed to predator cues from the muricid snail Acanthina monodon, while simultaneously exposing them to current (500 ppm) or projected OA conditions (1500 ppm). The response of purple mussels to these factors was assessed using growth, calcification, clearance, and metabolic rates, in addition to byssus production. After 60 d, the presence of predator cues reduced mussel growth in width and length, and in the latter case, OA enhanced this response making the effects of predator cues more severe. Calcification rates were driven by the interaction between the two stressors, whereas clearance rates increased only in response to OA, likely explaining some of the growth results. Mussel byssus production also increased with pCO2 but interacted with predation risk: in the absence of predator cues, byssus production increased with OA. These results suggest that projected levels of OA may alter and in some cases prevail over the natural response of purple mussels to predation risk. Considering the role played by this mussel as a dominant competitor and ecosystem engineer in rocky shores, these results have community-wide implications.

The Effect of Microplastics on the Bioenergetics of the Mussel Mytilus coruscus Assessed by Cellular Energy Allocation Approach

Marine microplastics pollution is a major environmental concern in marine ecosystems worldwide, yet the biological impacts of microplastics on the coastal biota are not yet fully understood. We investigated the impact of suspended microplastics on the energy budget of the mussels Mytilus coruscus using the Cellular Energy Allocation (CEA) approach. The mussels were exposed to control conditions (no microplastics) or to one of the three concentrations of 2 μm polystyrene microspheres (10, 104, and 106 particles/L) for 14 days, followed by 7 days of recovery. Exposure to high concentrations of microplastics (104 or 106 particles/L) increased cellular energy demand (measured as the activity of the mitochondrial electron transport system, ETS) and depleted cellular energy stores (carbohydrates, lipids, and proteins) in the mussels whereas exposure to 10 particles/L had no effect. Carbohydrate levels decreased already after 7 days of microplastics exposure and were restored after 7 days of recovery. In contrast, the tissue levels of lipids and proteins declined more slowly (after 14 days of exposure) and did not fully recover after 7 days following the removal of microplastics. Therefore, the total energy content and the CEA declined after 7–14 days of exposure to high microplastics concentrations, and remained suppressed during 7 days of subsequent recovery. These findings demonstrate a negative impact of microplastics on energy metabolism at the cellular level that cannot be restored during a short time recovery. Given a close link of CEA with the organismal energy balance, suppression of CEA by microplastics exposure suggests that bioenergetics disturbances might lead to decreases in growth and productivity of mussels’ populations in environments with heavy microplastics loads.

Depth drives growth dynamics of dreissenid mussels in Lake Ontario

Understanding dreissenid mussel population dynamics and their impacts on lake ecosystems requires quantifying individual growth across a range of habitats. Most dreissenid mussel growth rates have been estimated in nutrient rich or nearshore environments, but mussels have continued to expand into deep, cold, low-nutrient habitats of the Great Lakes. We measured annual quagga mussel (Dreissena rostriformis bugensis) growth at 15 m, 45 m, and 90 m in Lake Ontario using caged mussels near Oswego, New York, USA from June 2018 to May 2019. Quagga mussel growth (starting size 12 mm) was greatest at 15 m (mean shell length increase = 10.2 mm), and was lower at 45 m (5.9 mm) and 90 m (0.7 mm). Caged mussels were obtained from near the 90-m site and those reared at 15 and 45 m developed thicker shells than those that were caged at 90 m. We observed relatively high colonization by quagga and, to a lesser degree, zebra mussels (Dreissena polymorpha) at 15 m, very few colonizers at 45 m, and none at 90 m. Higher growth potential, but low natural mussel densities observed at 15 m and 45 m suggest factors other than growth limit dreissenid abundance at these depths. The relatively slow dreissenid growth rates observed in offshore habitats are consistent with the gradual abundance increases documented in these zones across the Great Lakes and suggest new mussels that become established in these habitats may contribute to ecosystem effects for decades.

Cyclic thermal fluctuations can be burden or relief for an ectotherm depending on fluctuations’ average and amplitude

Abstract Predicting the implications of ongoing ocean climate warming demands a better understanding of how short‐term thermal variability impacts marine ectotherms, particularly at beyond‐optimal average conditions during summer heatwaves. Using a globally important model species, the blue mussel Mytilus, in a 5‐week‐long experiment, we (a) assessed growth performance traits under 12 scenarios, consisting of four thermal averages (18.5, 21, 23.5 and 26℃) imposed as constant or daily fluctuating regimes with amplitudes of 2 or 4℃. Additionally, we conducted a short‐term assay using different mussel individuals to (b) test for the species capacity for suppression and recovery of metabolic performance traits (feeding and aerobic respiration) when exposed to a 1‐day thermal fluctuation regime (16.8–30.5℃). Using this high‐resolution data, we (c) generated short‐term thermal metabolic performance curves to predict and explain growth responses observed in the long‐term experiment. We found that daily high‐amplitude thermal cycles (4℃) improved mussel growth when fluctuations were imposed around an extreme average temperature of 26℃, representing end‐of‐century heatwaves. In contrast, thermal cycles negatively affected mussel growth at a less extreme average temperature of 23.5℃, resembling current peak summer temperature scenarios. These results suggest that fluctuations ameliorate heat stress impacts only at critically high average temperatures. The short‐term assay demonstrated that during the warming phase, animals stopped feeding between 24 and 30℃ while gradually suppressing respiration. In the subsequent cooling phase, feeding and respiration partially and fully recovered to pre‐heating rates respectively. Furthermore, nonlinear averaging of short‐term feeding responses (upscaling) well‐predicted longer term growth responses to fluctuations. Our findings suggest that fluctuations can be beneficial to or detrimental for the long‐term performance of ectothermic animals, depending on the fluctuations' average and amplitude. Furthermore, the observed effects can be linked to fluctuation‐mediated metabolic suppression and recovery. In a general framework, we propose various hypothetical scenarios of fluctuation impacts on ectotherm performance considering inter‐ or intra‐species variability in heat sensitivity. Our research highlights the need for studying metabolic performance in relation to cyclic abiotic fluctuations to advance the understanding of climate change impacts on aquatic systems. A free Plain Language Summary can be found within the Supporting Information of this article.

Investigation of the potential of liposome and microparticulate feeds to partially replace microalgae in the nursery rearing of green‐lipped mussels ( Perna canaliculus )

The seeding of small juvenile green-lipped mussels (Perna canaliculus) onto coastal farms is associated with high losses. These losses can be reduced by seeding larger juveniles; however, the nursery culture of juveniles is unviable because of the high cost of producing live microalgal feeds. In this study, we compared the ability for two diets, a formulated microparticulate feed, MySpat and liposomes fabricated with mussel extract to replace live microalgae at different proportions for feeding small (1.9 mm shell length ±0.02 SE) green-lipped mussels. The experimental diets consisted of a mix of live Tisochrysis lutea, Diacronema lutheri and Chaetoceros muelleri that were replaced with increasing proportions of MySpat (25%, 50% and 75%), and liposomes (25% and 50%). There were no significant differences in mortality of mussels relative to the control (100% microalgae) among any of the diet treatments. However, mussel growth tended to decrease with increasing substitution of the microalgal component of the diets. The results from this study suggest that microparticulate and liposome formats provide a viable mode of food delivery to juvenile mussels, with improved formulation of these formats having the potential to lead to the substitution of live microalgal diets which make nursery culture unviable at present.

Effects of dissolved oxygen concentrations on growth, survival and gonadal development of freshwater pearl mussel Lamellidens marginalis

The present study was conducted to evaluate the effects of dissolved oxygen concentrations on growth, survival and gonadal development of freshwater pearl mussel (Lamellidens marginalis). Twenty adult L. marginalis were exposed to each of the five different concentrations of dissolved oxygen (DO) i.e (T0, no aeration), and T1, T2, T3 and T4 with one, two, three and four air stone aerators, respectively in fifteen glass aquaria each containing 10L of pond water. DO concentrations were significantly higher in all the treatments compared to the control but there were no significant differences among the treatments. There were significant differences in the growth and survival rates between control and treatments. The relative growth rates (%) were significantly higher in the highest oxygen concentration (T4) compared to other treatments. The survival rate was zero in control (T0), whereas it was 66.67%, 70.00%, 71.67% and 73.33%, respectively for T1, T2, T3 and T4. On day-30, oocytes in T0 were found to be smaller in size, with developing acini and no previtellogenic oocytes; whereas in T1, T2, T3 and T4, previtellogenic oocytes and larger acini were evident. On day-60, vitellogenic oocytes along with few under-developed oocytes started to detach from the acini walls, as well as some already started migration to germinal duct on day-90. This indicates that ovaries of all the treatments were ripe and were ready to spawn between day-60 and -90. On day-30, secondary spermatocytes were observed in testicular acini in case of T0, whereas more developed and dense spermatids were evident in T1, T2, T3 and T4. These results indicate that testes were in late development stages in T0, whereas they were ripe in all the treatments. The current findings indicate that hypoxia slows down growth, reduces survival rate and retards development of reproductive organs in L. marginalis.

Estuarine oiling increases a long-term decline in mussel growth

The ribbed mussel, Geukensia granosissima, cycles nutrients, contributes to soil stability, and can be a major component of predator-prey communities in salt marshes. Mussels were exposed to the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, and salt marshes remain contaminated eight years later. We hypothesized that the oiled mussels had reduced annual growth, altered population size frequency, and perhaps changed valve morphometrics. We sampled 10 marshes near Port Sulphur, LA, to measure the morphometrics of 133 mussels and their age-specific growth rate, and also the marsh oil content and percent vegetative cover. The relationships between valve weight, length and biomass weight were stable as mussels aged. A Year 1 growth decline from 1994 to 2018 is not easily explained by estuarine acidification, flooding, and temperature rise; freshening of estuarine waters is suggested to be a probable causal factor in the declining growth rate. The average valve length and dry biomass per valve declined with oiling in 2010. A multiple regression equation using the percent cover and oil concentration in 2018 described 70% of the variation in valve length. Sites with the highest oiling had few mussels with 14 annual growth bands and more of the younger mussels compared to sites with the lowest oiling. Valve growth in Year 1 declined for four years after the oil spill and was not compensated by higher growth rates in older mussels. Annual growth was below the amount predicted in a regression equation for the five years after the oil spill. Mussel populations may also have been structured by predators that were also responsive to oiling in subtle ways.

Shell morphology, growth and longevity of Unio tumidus (Bivalvia: Unionidae) from an archaeological site and contemporary population inhabiting the Oder estuary

Mussel shells are often found in archaeological excavations and can provide information useful for ecological reconstruction and assessment of anthropogenic impact on waters. In this study, two sample groups of swollen river mussel (Unio tumidus) which occurred during the Early Middle Ages (EMS) and currently (MS) in the Oder river estuary (Baltic basin) were compared. Allometric shell growth, morphological characteristics of the shell (length, width, height and thickness), age structure and growth of mussels were analysed using the von Bertalanffy equation. All three types of allometric growth (isometry and both positive and negative allometry) were observed in the studied mussels. In both groups, typical values of shell length, width, height and thickness were recorded. However, higher values of these morphological characteristics were recorded in the EMS group. Moreover, the EMS group, compared with the MS group of U. tumidus, was characterised by a higher longevity (12 and 10 years, respectively) and asymmetric length (L∞) (93.09 and 83.23 mm, respectively). Both groups of mussels had a similar growth rate (k). Larger shell sizes in the EMS group were probably caused by differential preservation and/or differential archaeological recovery, and resulted from differences in the age structure, especially higher mortality rate amongst individuals older than 6 years in the MS group.

-Blue mussel (Mytilus spp.) cultivation in mesohaline eutrophied inner coastal waters: mitigation potential, threats and cost effectiveness.

The EU-water framework directive (WFD) focuses on nutrient reductions to return coastal waters to the good ecological status. As of today, many coastal waters have reached a steady state of insufficient water quality due to continuous external nutrient inputs and internal loadings. This study focuses first on the current environmental status of mesohaline inner coastal waters to illustrate their needs of internal measures to reach demanded nutrient reductions and secondly, if mussel cultivation can be a suitable strategy to improve water quality. Therefore, nitrogen, phosphorus, chlorophyll a, and Secchi depth of nine mesohaline inner coastal waters in north east Germany were analyzed from 1990 to 2018. Two pilot mussel farms were used to evaluate their effectiveness as a mitigation measure and to estimate potential environmental risks, including the interactions with pathogenic vibrio bacteria. Further, estimated production and mitigation potential were used to assess economic profitability based on the sale of small sized mussels for animal feed and a compensation for nutrient mitigation. The compensation costs were derived from nutrient removal costs of a waste water treatment plant (WWTP). Results show that currently all nine water bodies do not reach the nutrient thresholds demanded by the WFD. However, coastal waters differ in nutrient pollution, indicating that some can reach the desired threshold values if internal measures are applied. The mitigation potential of mussel cultivation depends on the amount of biomass that is cultivated and harvested. However, since mussel growth is closely coupled to the salinity level, mussel cultivation in low saline environments leads to lower biomass production and inevitably to larger cultivation areas. If 50% of the case study area Greifswald Bay was covered with mussel farms the resulting nitrogen reduction would increase Secchi depth by 7.8 cm. However, high chlorophyll a values can hamper clearance rates (<20 mg m−3 = 0.43 l h−1 dry weight g−1) and therefore the mitigation potential. Also, the risk of mussel stock loss due to high summer water temperatures might affect the mitigation potential. The pilot farms had no significant effect on the total organic content of sediments beneath. However, increased values of Vibrio spp. in bio deposits within the pilot farm (1.43 106 ± 1.10 106CFU 100 ml−1 (reference site: 1.04 106 ± 1.45 106 CFU 100 ml−1) were measured with sediment traps. Hence, mussel farms might act as a sink for Vibrio spp. in systems with already high vibrio concentrations. However, more research is required to investigate the risks of Vibrio occurrence coupled to mussel farming. The economic model showed that mussel cultivation in environments below 12 PSU cannot be economic at current market prices for small size mussels and compensations based on nutrient removal cost of WWTPs.

Environmental controls on long-term growth of freshwater mussels in an oligotrophic lake

Freshwater mussels are one of the most endangered groups of animals and live in some of the fastest changing ecosystems in the world. Unfortunately, very little is known about how their life history and ecology are influenced by their environment, especially for lake-dwelling populations. In this study, we paired ∼30 y of extensive environmental data to lifetime and annual growth rates of a population of Fatmucket mussels (Lampsilis siliquoidea) living in a cool-water oligotrophic lake in northern Wisconsin, USA. This population displayed one of the slowest growth rates and longest lifespans within its phylogenetic tribe (Lampsilini). Growth rates were highly variable between individuals and, in contrast to studies in other systems, not related to temperature, growing season, or any indicators of primary production. However, growth rates were positively correlated with changes in lake level. We hypothesize that mussel growth in this system is linked to landscape-level environmental conditions and allochthonous resource limitation.

Resource allocation to a structural biomaterial: Induced production of byssal threads decreases growth of a marine mussel

Abstract The biomechanics of specialized mechanical structures produced by organisms provides crucial fitness advantages. The energetic cost associated with producing these structural materials and the resulting energetic trade‐off with growth, however, is rarely quantified. We integrate resource allocation to structural material production with an energetic framework by combining an experimental manipulation with an energetic model. Mytilid bivalves produce byssus, a network of collagen‐like threads that tethers individuals to hard substrate. We hypothesized that a manipulation that induces the production of more byssal threads would result in increased energetic cost and decreased growth of the species Mytilus trossulus. In month‐long field experiments in spring and autumn, we severed byssal threads across a range of frequencies (never, weekly, daily), and measured shell and tissue growth. We then quantified the costs associated with the production of byssal threads using a Scope for Growth model. We found that byssal thread removal increased byssal thread production and decreased growth. The cost calculated per byssal thread was similar in the spring and autumn (~1 J/thread), but energy budget calculations differed by season, and depended on thread quantity and seasonal differences in assumptions of metabolic costs. This work demonstrates that the cost of producing a structural material has a substantial effect on mussel energetic state. The energetic cost of producing byssal threads was 2%–8% percent of the energy budget in control groups that had low byssal thread production, and increased six to 11‐fold (up to 47%) in mussels induced to produce threads daily. We propose that characterizing the trade‐off between the cost of biomaterial production and growth has implications for understanding the role of trade‐offs in adaptive evolution, and improved natural resource management and conservation practices. A free Plain Language Summary can be found within the Supporting Information of this article.

Coastal foraging on the West Coast of South Africa in the midst of mid-Holocene climate change

The mid-Holocene (ca. 8200–4200 cal BP) brought about important climatic changes and environmental shifts to land and coastal systems, globally. Many of the human groups existing at that time were affected in various degrees by such important modifications to their foraging areas, including shorelines. Higher sea-levels (+1–3 m) were a prominent factor reshaping coastal landscapes and thus affecting coastal foraging in one or more ways. Hot and dry weather and relatively higher sea levels along the central west coast of South Africa impacted substantially on local coastal hunter-gatherer groups. These challenges were thought once to have been unsurmountable because of an apparent absence of sites dated to this period. Recently dated mid-Holocene assemblages allow us to gain insight into coastal resource procurement and overall subsistence, and also to derive more detailed coastal paleoecological data. The results show a predominantly terrestrial diet, while shellfish collection persisted amid prevailing environmental factors affecting mussel growth by supplementing their reduced mollusk takes with additional prey. Sizeable crustaceans were also procured in relatively large numbers in some localities, but not in all. This is the most-up-to date mid-Holocene subsistence record for the central west coast of South Africa which, apart from reconstructing changes in procurement strategies, reveals a trajectory of persistence in the face of climate change.

The combined effects of climate change stressors and predatory cues on a mussel species

In order to make adequate projections on the consequences of climate change stressors on marine organisms, it is important to know how impacts of these stressors are affected by the presence of other species. Here we assessed the direct effects of ocean warming (OW) and acidification (OA) along with non-consumptive effects (NCEs) of a predatory crab and/or a predatory snail on the habitat-forming mussel Perumytilus purpuratus. Mussels were exposed for 10–14 weeks to contrasting pCO2 (500 and 1400 μatm) and temperature (15 and 20 °C) levels, in the presence/absence of cues from one or two predator species. We compared mussel traits at sub-organismal (nutritional status, metabolic capacity-ATP production-, cell stress condition via HSP70 expression) and organismal (survival, oxygen consumption, growth, byssus biogenesis, clearance rates, aggregation) levels. OA increased the mussels' oxygen consumption; and OA combined with OW increased ATP demand and the use of carbohydrate reserves. Mussels at present-day pCO2 levels had the highest protein content. Under OW the predatory snail cues induced the highest cell stress condition on the mussels. Temperature, predator cues and the interaction between them affected mussel growth. Mussels grew larger at the control temperature (15 °C) when crab and snail cues were present. Mussel wet mass and calcification were affected by predator cues; with highest values recorded in crab cue presence (isolated or combined with snail cues). In the absence of predator cues in the trails, byssus biogenesis was affected by OA, OW and the OA × OW and OA × predator cues interactions. At present-day pCO2 levels, more byssus was recorded with snail than with crab cues. Clearance rates were affected by temperature, pCO2 and the interaction between them. The investigated stressors had no effects on mussel aggregation. We conclude that OA, OW and the NCEs may lead to neutral, positive or negative consequences for mussels.

Modeling the impact of climate change on mussel aquaculture in a coastal upwelling system: A critical assessment

Forecasting of climate change impacts on marine aquaculture production has become a major research task, which requires taking into account the biases and uncertainties arising from ocean climate models in coastal areas, as well as considering culture management strategies. Focusing on the suspended mussel culture in the NW Iberian coastal upwelling system, we simulated current and future mussel growth by means of a multistructural net production Dynamic Energy Budget (DEB) model. We considered two scenarios and three ocean climate models to account for climate uncertainty, and applied a bias correction to the climate models in coastal areas. Our results show that the predicted impact of climate change on mussel growth is low compared with the role of the seeding time. However, the response of mussels varied across climate models, ranging from a minor growth decline to a moderate growth increase. Therefore, this work confirms that an accurate forecasting of climate change impacts on shellfish aquaculture should take into account the variability linked to both management strategies and climate uncertainty.

Growth patterns of the pan-European freshwater mussel, Anodonta anatina (Linnaeus, 1758) (Bivalvia: Unionidae), vary with sex and mortality in populations.

Post‐maturation growth leading to indeterminate growth patterns is widespread in nature. However, its adaptive value is unclear. Life history theory suggests this allocation strategy may be favored by temporal pulses in the intensity of mortality and/or the capacity to produce new tissues.Addressing the origin of indeterminate growth and the variability of growth patterns, we studied the growth of duck mussels, Anodonta anatina, a pan‐European unionid, in 18 Polish lakes. For each population, the sex, size, and age of collected mussels were measured to estimate Bertalanffy's growth curve parameters. We integrated information on A. anatina mortality rates, lake trophy, biofouling by zebra mussels, Dreissena polymorpha, and the prevalence of parasitic trematode larvae to identify selective conditions in lakes.We found two sources of mortality in A. anatina populations, pertaining to adverse effects of zebra mussel biofouling and trophy state on mussel survival. Additionally, populations with heavier biofouling presented a smaller abundance of parasites, indicative of a relationship between filtering intensity and contraction of water‐borne trematode larvae by filtering A. anatina.Consistently for each sex, populations with a greater trophy‐related mortality were characterized in A. anatina by a smaller asymptotic size Lmax, indicative of a life history response to mortality risk involving early maturation at a smaller body size. In all populations, females featured higher mortality and larger asymptotic size versus males.Our findings support a theoretical view that adaptive responses to selection involve adjustments in the lifetime resource allocation patterns. These adjustments should be considered drivers of the origin of indeterminate growth strategy in species taking parental care by offspring brooding in body cavities.

Density and characteristics of Green mussels (Perna viridis) in Percut Sei Tuan coastal, North Sumatra, Indonesia

Percut Sei Tuan is a coastal area on the east coast of North Sumatra which has a lot of natural resource potential, one of them which is green mussels (Perna viridis). Green mussels have many benefits, namely for consumption, cultivation and bioindicator. This study aimed to determine the density, habitat location, growth pattern, frequency distribution of green mussels, physical-chemical parameters of water, a substrate of the bottom waters, and the relationship of green clams density to water and substrate parameters. The study was conducted in July-September 2020. Data analysis included density, the relationship of total length and weight of green mussels, the frequency distribution of shell lengths, and Principal Component Analysis (PCA). The results showed that the density of green mussels at stations I, II, and III were 352 ind/m2, 3 ind/m2, and 1 ind/m2, respectively. The relationship between the length and weight of green shells shows that the growth was negative allometric. The water condition, seen from the physical, chemical, and substrate parameters, was still suitable for P. viridis. Water and substrate parameters that were positively related to the density of green mussels were water temperature, nitrate, phosphate, C-organic, percentage of silt and clay. Parameters that were negatively related were salinity, pH, and percentage of sand in the bottom substrate. The present study suggested that Station I was an appropriate area for the growth and reproduction of green mussels.

Effects of in vitro metamorphosis on survival, growth, and reproductive success of freshwater mussels

Captive breeding is an effective conservation strategy, but it has risks, especially when a life history stage of an organism is bypassed. Freshwater mussels (Unionida) are critically imperiled, and their larvae are parasites on fishes. Traditional mussel captive breeding involves artificially infesting fishes with larvae (in vivo), but increasingly used in vitro methods allow larval metamorphosis in culture media, bypassing the parasitic stage. We provide the first comparisons of mussel performance between in vitro and in vivo methods in the wild and throughout the mussel life cycle using two mussel species. In six streams, survival and growth did not differ between in vitro- and in vivo-produced Lampsilis cardium. Metamorphosis of Sinanodonta woodiana differed sharply between two in vitro protocols (methods 1 and 2), but metamorphosis for method 2 was twice as high as in vivo. Survival and growth after eight days was lower for in vitro method 1 than method 2 and in vivo, showing that suboptimal in vitro protocols can have lingering effects on juvenile performance. However, survival and growth did not differ among methods by the end of the first and second growing seasons. Most importantly, in vitro-produced mussels survived, grew to maturity, and produced F2 juveniles naturally on fishes, all at rates that did not differ from in vivo-produced mussels. We detected no strong side effects of bypassing the mussel host-fish stage, but this study illustrates the importance of assessing consequences of captive breeding methods for any organism in a variety of environmental and life history contexts.

Modelling effects of seaweed aquaculture on phytoplankton and mussel production. Application to Strangford Lough (Northern Ireland)

Coupled macroalgal-phytoplankton and shellfish models were used to investigate the effect of macroalgae cultivation on phytoplankton and mussel growth in Strangford Lough, Northern Ireland. The study focused on the kelp species Saccharina latissima for which observational data were available from rope deployments at an experimental seaweed farm. The calibrated model gave good agreement with observed nutrient and chlorophyll concentrations as well as matching observation of kelp growth rates and frond area. Timing of spring phytoplankton growth and subsequent nutrient drawdown in the model was found to have a large effect (~50% change) on predicted kelp frond area in summer. The model was used to investigate the effect of light shading and nutrient competition between farmed S. latissima and phytoplankton (a key food source for shellfish) for a range of farm sizes. Simulations showed that kelp farming had minor impacts in general but that very intensive farming over an extensive area could lead to significant decreases in phytoplankton and mussel biomass. Simple criteria were developed for estimating the size and density of macroalgal farming that would lead to significant nutrient competition with phytoplankton. Modelling in the strong nutrient competition regime with a hypothetical very high intensity farm occupying 22% of the Lough surface, gave decreases in spring/summer phytoplankton chlorophyll concentrations of 11% (nutrient competition only) and 23% (nutrient competition and light shading). The impact on harvested dry weight of mussels is similar but smaller, with decreases of 4% (nutrient competition) and 10% (light and nutrient competition). It should be noted these are based on model compartment averages and localised changes, not resolved by the model, may be higher.