Mussel Growth Research Articles

APPLICATION OF INTEGRATED MULTI TROPIC AQUACULTURE CONCEPT IN AN ABRADED BRACKISH WATER POND

Currently, abrasion at the northern coastline of Central Java, Indonesia, is severe. One of the biggest abrasion area is in Kaliwlingi village (Brebes District), where 800 ha of brackish water ponds were submerged. Abrasion could wipe away or damage dykes on brackish water pond and the pond can no longer be used for aquaculture production. A 5 000 m2 of netting broken dyke of brackish water pond is used for semi–intensive cultivation of milkfish, tilapia, vanamae shrimp, green mussel and Gracilaria seaweed as an application of Integrated Multi Trophic Aquaculture (IMTA) concept. The aim of this study was to determine the aquaculture production in abraded dyke on brackish water pond by measuring the growth of milk fish, tilapia, vaname shrimp, green mussel and Gracilaria based on IMTA concept. The study was carried out from May to July 2015 at Kaliwlingi Village, Brebes district. The results showed Specific Growth Rate (SGR), i.e. milk fish 2.35 % d–1; tilapia 3.8 %·d–1 vanamae shrimp 3.75 % d–1; green mussel 2.8 % d–1 and Gracilaria 4.6 % d–1. Based on the result, the water quality is good and the availability of the natural food can support the growth of milkfish, tilapia, vanamae shrimp, green muscle and seaweed at broken dyke ponds with IMTA concept.

Picophytoplankton contribution to Mytilus edulis growth in an intensive culture environment

Autotrophic picoplankton (≤2.0 µm) is one of the most abundant phytoplankton components in marine ecosystems. The contribution of picophytoplankton to blue mussel (Mytilus edulis) growth was investigated in eastern Prince Edward Island, where the bulk of the Canadian suspended mussel industry is located. Field trials using flow cytometry were used to determine the ability of mussels to retain picophytoplankton (0.2–2.0 µm) and nanophytoplankton (2.0–20.0 µm). Size-fractionated phytoplankton biomass (chl-a) and mussel growth (shell height and tissue weight) were also measured. Mussel retention efficiencies (RE) for picophytoplankton and nanophytoplankton averaged 20 ± 2.0 and 60 ± 3.5 %, respectively. Estimates of RE and phytoplankton biomass were integrated into a dynamic energy budget (DEB) model to investigate the contribution of picophytoplankton to mussel growth during the post-spring bloom period. When DEB simulations excluded picophytoplankton (RE = 0 %), the predicted reduction in mussel growth ranged between 14 and 29 %. It is concluded that the contribution of <2.0-µm phytoplankton to the mussel’s energy budget is non-negligible and should be taken into account when investigating interactions between bivalve farming and phytoplankton dynamics.

High mortality and poor growth of green mussels, Perna viridis, in high chlorophyll-a environment

The current study was carried out from May 2014 to April 2015 to estimate the stock status of P. viridis in Marudu Bay. The gonad development was monitored by histological examination, while the population parameters including asymptotic length (L ∞), growth coefficient (K), mortality rate (Z, F and M), exploitation level (E) and recruitment of P. viridis were estimated using the lengthfrequency data. Results of the current study demonstrated that P. viridis in Marudu Bay spawned throughout the year with two major peaks, one in April to May and another one in October to December. The recruitment pattern was continuous with the peak in May to June 2014, which corresponded to the first spawning peak in April. However, no significant recruitment was observed from the second spawning peak due to the difference in spawning timing between male and female populations. The estimated asymptotic length (L ∞), growth coefficient (K), total mortality (Z), natural mortality (M), fishing mortality (F) and growth performance (ф) of P. viridis in Marudu Bay were estimate to be 117 mm, 0.97 yr-1, 4.39 yr-1, 1.23 yr-1, 3.16 yr-1 and 4.123, respectively. The exponent b of the lengthweight relationship was 2.4 and exploitation level (E) was 0.72. The high mortality, low condition indices and negative allometric of P. viridis in Marudu Bay is caused by a lack of suitable food in the surrounding water.

Environmental influence on mussel (Mytilus edulis) growth – A quantile regression approach

The need for methods for sustainable management and use of coastal ecosystems has increased in the last century. A key aspect for obtaining ecologically and economically sustainable aquaculture in threatened coastal areas is the requirement of geographic information of growth and potential production capacity. Growth varies over time and space and depends on a complex pattern of interactions between the bivalve and a diverse range of environmental factors (e.g. temperature, salinity, food availability). Understanding these processes and modelling the environmental control of bivalve growth has been central in aquaculture. In contrast to the most conventional modelling techniques, quantile regression can handle cases where not all factors are measured and provide the possibility to estimate the effect at different levels of the response distribution and give therefore a more complete picture of the relationship between environmental factors and biological response. Observation of the relationships between environmental factors and growth of the bivalve Mytilus edulis revealed relationships that varied both among level of growth rate and within the range of environmental variables along the Swedish west coast. The strongest patterns were found for water oxygen concentration level which had a negative effect on growth for all oxygen levels and growth levels. However, these patterns coincided with differences in growth among periods and very little of the remaining variability within periods could be explained indicating that interactive processes masked the importance of the individual variables. By using quantile regression and local regression (LOESS) this study was able to provide valuable information on environmental factors influencing the growth of M. edulis and important insight for the development of ecosystem based management tools of aquaculture activities, its use in mitigation efforts and successful management of human use of coastal areas.

Reconsidering evidence of human impacts: Implications of within-site variation of growth rates in Mytilus californianus along tidal gradients

Abstract Disentangling the complex web of human and natural effects that structure archaeological shellfish assemblages remains a challenging process that requires careful consideration of interdisciplinary datasets. The ecological data presented in this paper demonstrate highly variable growth rates within intertidal patches of Mytilus californianus . These results fill a spatial and conceptual gap in our understanding of small-scale variability in mussel growth rates and terminal shell size, and have significant implications for understanding ancient human foraging behavior, as well as how we interpret archaeological signatures of anthropogenic impact on mussel populations. We evaluate how small-scale variation along tidal gradients structures the size of resources available to coastal foragers throughout the lunar cycle. This ecological study leads us to propose that increased exploitation of smaller mussels available at higher shore levels during less favorable tides could result in archaeological assemblages that mimic the expected correlates for resource depression, thus, confounding interpretation of human impacts.

Long-term exposure to fluoxetine reduces growth and reproductive potential in the dominant rocky intertidal mussel, Mytilus californianus

Environmental stressors shape community composition and ecosystem functioning. Contaminants such as pharmaceuticals are of increasing concern as an environmental stressor due to their persistence in surface waters worldwide. Limited attention has been paid to the effects of pharmaceuticals on marine life, despite widespread detection of these contaminants in the marine environment. Of the existing studies, the majority assess the negative effects of pharmaceuticals over an exposure period of 30days or less and focus on cellular and subcellular biomarkers. Longer studies are required to determine if chronic contaminant exposure poses risks to marine life at environmentally relevant concentrations; and examination of whole organism effects are necessary to identify potential community-level consequences in estuarine and marine ecosystems. We conducted a long-term exposure study (107days) with the anti-depressant pharmaceutical, fluoxetine (the active constituent in Prozac®) to determine whether minimal concentrations affected whole organism metrics in the California mussel, Mytilus californianus. We measured algal clearance rates, mussel growth, and the gonadosomatic index, a measure of reproductive health. We found that fluoxetine negatively affects all measured characteristics, however many effects were mediated by length of exposure. Our results fill an important data gap, highlighting organism-level effects of chronic exposure periods; such data more explicitly identify the overall impacts of pharmaceuticals and other contaminants on marine communities and ecosystems.

Growth, biochemical profile, and fatty acid composition of mussel (Mytilus galloprovincialis Lmk.) cultured in the open ocean of the Bay of Biscay (northern Spain)

Growth performance, allometry, condition index, and biochemistry of mussel (Mytilus galloprovincialis Lmk.) cultured in a submerged longline system were investigated from June 2013 to August 2014. Mussels grew faster from spring to autumn. Chlorophyll-a concentration along with sea current speed will represent major factors controlling mussel seasonal growth and survival success in the case-study region. The lowest condition indices and highest ash contents were respectively found within winter; so the most favorable conditions for mussel harvesting and commercialization operations would tentatively occur within autumn, spring and summer. The positive mussel growth and low chlorophyll-a concentrations found during summer may also indicate utilization of non-phytoplankton food sources. No clear evidence of local depth associated physiological effects on the mussel individuals was detected. This contribution represents the first available information on open ocean mussel aquaculture from the southeastern Bay of Biscay. Statement of relevance(1.)The present contribution fills a noticeable gap in the literature on mussel biology and aquaculture science in the Bay of Biscay.(2.)The present contribution reports the first technical and scientific success of open ocean mussel aquaculture practices in the Bay of Biscay.(3.)The present contribution offers scientific information for further data comparisons within the context of other case studies or hypothesis.(4.)The present contribution offers valuable information for decision-making processes on commercial open ocean aquaculture.

Modeling and predicting the growth of the mussel, Mytilus edulis: implications for planning of aquaculture and eutrophication mitigation.

The increased pressure on the marine ecosystems highlights the need for policies and integrated approaches for sustainable management of coastal areas. Spatial planning based on geographic information of human activities, ecological structures and functions, and their associated goods and services is a fundamental component in this context. Here, we evaluate the potential of predictive modeling to provide spatial data on one ecosystem function, mussel growth for use in such processes. We developed a methodology based on statistical modeling, spatial prediction, and mapping for the relative growth of the blue mussel, Mytilus edulis. We evaluated the performance of different modeling techniques and classification schemes using empirical measurements of growth from 144 sampling sites and data on biological, chemical, and physical predictors. Following comparisons of the different techniques and schemes, we developed random forest models to predict growth along the Swedish west coast. Implemented into GIS the best model produced in this study predicts that low, intermediate, and high growth rates can be expected in 53%, 32%, and 15% of modeled area, respectively. The results of this study also suggest that the nature and quality of predictor data hold the key to improving the predictive power of models. On a more general note, this study exemplifies a feasible approach based on measuring, modeling, and mapping for obtaining scientifically based spatial information on ecosystem functions and services affected by a complex set of factors. Such information is fundamental for maritime spatial planning and ecosystem-based management and its importance is likely to increase in the future. Because of its close link to nutrient assimilation and production yield, site-specific information of soft tissue growth such as the map of predicted growth rate developed in this study can be used as a tool for optimizing actions aimed at mitigating eutrophication and aquaculture operations and in maritime spatial planning processes of coastal areas.

Effective growth cessation in adult Unio crassus Philipsson, 1788 (Bivalvia: Unionidae) from Germany

Information on the growth and age of the endangered freshwater mussel Unio crassus Philipsson, 1788 is crucial to correctly assess the conservation status of a particular population. This long-term study of individually marked specimens from four populations from central and southwest Germany revealed that zero growth and shrinkage of adult mussels from the upper 50% of their population’s length range were common phenomena. Therefore, overall shell length measurements or counting of growth lines on the shells of live adult mussels may grossly underestimate their age and should be regarded as unsuitable for determining the actual age structure of a population. Key wOrDs: growth cessation, age determination, long-term study, Unio crassus, Unionidae

Successful survival, growth, and reproductive potential of quagga mussels in low calcium lake water: is there uncertainty of establishment risk?

The risk of quagga mussel (Dreissena rostriformis bugensis Andrusov 1897) establishment into water-bodies of the western US has expanded the geographic concern regarding the ecological and economic impacts this species will have in aquatic ecosystems. Thresholds based on calcium concentrations, an element critical for mussel growth and physiology, have been used as a primary predictor of quagga mussel establishment success to aid management decisions. We evaluated the invasion potential of quagga mussels in low calcium waters using laboratory experiments to compare the survival, growth and reproductive potential of adult mussels held for 90 days at low (9 and 12 ppm), moderate (15 to 32 ppm) and high (72 ppm) calcium water concentrations. In conjunction with adult experiments, veliger stage survival, growth and settlement were evaluated under similar low, moderate, and high calcium water treatments. Adult mussels survived, grew and showed reproductive potential in low calcium water (12 ppm). Veligers were also able to survive, grow and settle in low calcium water. Higher levels of natural seston biomass appeared to improve adult mussel life history performance in low calcium water. Survival curve analysis predicted that 99% adult mortality could occur in <170 days at 9 ppm and 12 ppm, however water with >15 ppm could have adults surviving more than a year. The results from these bioassays provide further evidence that quagga mussels have higher risk of establishment in low calcium lakes if habitats exist that have slightly elevated calcium. These results should help emphasize the vulnerability of water-body in the 12 to 15 ppm calcium range that could potentially be at risk of establishing sustainable quagga mussel populations. Furthermore, these results provide insights into the uncertainty of using a single parameter in assigning establishment risk given the complexity of variables in specific water-bodies that influence life history performance of introduced species.

Bathymodiolus growth dynamics in relation to environmental fluctuations in vent habitats

The deep-sea mussel Bathymodiolus thermophilus is a dominant species in the East Pacific Rise (EPR) hydrothermal vent fields. On the EPR volcanically unstable area, this late colonizer reaches high biomass within 4–5 years on new habitats created by lava flows. The environmental conditions and growth rates characterizing the reestablishment of B. thermophilus populations are however largely unknown, leaving unconstrained the role of this foundation species in the ecosystem dynamics. A typical example from the vent field at 9°50’N that was affected by the last massive eruption was the Bio-9 hydrothermal vent site. Here, six years later, a large mussel population had reestablished. The von Bertalanffy growth model estimates the oldest B. thermophilus specimens to be 1.3 year-old in March 2012, consistent with the observation of scarce juveniles among tubeworms in 2010. Younger cohorts were also observed in 2012 but the low number of individuals, relatively to older cohorts, suggests limited survival or growth of new recruits at this site, that could reflect unsuitable habitat conditions. To further explore this asumption, we investigated the relationships between mussel growth dynamics and habitat properties. The approach combined sclerochronology analyses of daily shell growth with continuous habitat monitoring for two mussel assemblages; one from the Bio-9 new settlement and a second from the V-vent site unreached by the lava flow. At both vent sites, semi-diurnal fluctuations of abiotic conditions were recorded using sensors deployed in the mussel bed over 5 to 10 days. These data depict steep transitions from well oxygenated to oxygen-depleted conditions and from alkaline to acidic pH, combined with intermittent sulfide exposure. These semi-diurnal fluctuations exhibited marked changes in amplitude over time, exposing mussels to distinct regimes of abiotic constraints. The V-vent samples allowed growth patterns to be examined at the scale of individual life and compared to long-term records of habitat temperature and oceanographic mooring data in the years following the eruption. Both shell growth and habitat temperature at V-vent varied over the spring-neap tidal cycle and over longer periods of c.a. 60 days. The correlation of growth rate with temperature and, for some individuals, with current velocities supports the idea that tidal forcing impacts growth. Its influence on habitat conditions includes the spring-neap cycle, which is not reflected in current velocities but influences the venting rate. Additionally, it is expected that mesoscale eddies periodically passing across the ridge imprint shell growth through the influence of bottom current on the decimeter-thick mixing interface where mussels thrive. We conclude that diurnal-semidiurnal tidal fluctuations exert major abiotic constraints on B. thermophilus mussels and that low-frequency fluctuations act as significant determinants on growth. Finally, we postulate that the modulation of tidal fluctuations by large-scale hydrodynamic forcing ultimately constrains the capacity of this mussel species to form high biomass aggregations. This study indeed shows that the absence of these strong hydrodynamic drivers would limit the alternance of oxic and sulfidic conditions and significantly affect the growth rate of this species over time.

Effects of substrate size and cleaning regime on growth and survival of captive-bred juvenile freshwater pearl mussels, Margaritifera margaritifera (Linnaeus, 1758)

The freshwater pearl mussel is critically endangered and most English populations are at risk of extinction unless conservation measures are implemented immediately. The study objectives were to test a culture system for rearing Margaritifera margaritifera in captivity, and to investigate the effects of substrate size (0.25–1 and 1–2 mm) and cleaning regime (weekly and monthly) on survival and growth. In total, 1207 and 518 juveniles were reared to 362 (12 months) and 758 days (25 months), respectively. After 362 days, survival was significantly higher in 1–2 mm substrate treatments cleaned monthly (55 ± 6 %) and lowest in 0.25–1 mm substrate cleaned weekly (14 ± 3 %). Growth was significantly higher in 1–2 mm substrates cleaned weekly (length = 1.15 ± 0.21 mm) and lowest in 0.25–1 mm substrates cleaned monthly (length = 0.83 ± 0.23 mm). Juveniles from most treatments did not display size-dependent over-winter survival, but a significant correlation was found between shell length and survival in the 0.25–1 mm weekly treatment. This low-maintenance system utilised features of previously described systems and growth and survival rates were comparable to, if not better than, other studies culturing M. margaritifera. The system could be scaled up to rear significant numbers of juveniles in captivity.

Seasonal assessment of biological indices, bioaccumulation and bioavailability of heavy metals in mussels Mytilus galloprovincialis from Algerian west coast, applied to environmental monitoring

Summary The aim of the present work is to broaden our knowledge on the variability of trace metals in mussel tissues, focusing on seasonal fluctuations in the three different sampling sites of Algerian west coast (Oran Harbor (S1), Ain Defla (S2) and Hadjaj (S3)). For this purpose, the bioavailability (metal indices) and bioaccumulation (metal concentrations in soft tissues) of heavy metals (Zn, Cu, Pb, and Cd), and the physiological characteristics (e.g. biological indices such as condition index (CI)) of mussels Mytilus galloprovincialis have been assessed and related to seasons and sites. In S1, the highest levels of metal concentrations and indices were obtained in mussels sampled in winter for Zn, Cu and Cd, but in summer for Pb. The biological indices significantly decreased in winter. In S2, the levels of concentrations and indices of all metals varied whatever the seasons, excepting in summer where the values were the lowest. In summer and spring, the biological indices were lower than in autumn and winter. The low growth of organisms in spring and summer might be correlated to the reproductive period and the low trophic level known in S2. S3, considered as a “pristine” area, showed low metal concentrations and indices, and high biological indices, reflecting the favorable physiological conditions for the mussel growth. This approach might be used in the monitoring of the quality of coastal waters and the present work provided a useful data set for Mediterranean monitoring network.

Type III functional response in the zebra mussel,Dreissena polymorpha

Distinguishing between functional response types requires observations at low food concentrations, but surprisingly these tend to be rare. A paucity of feeding observations at low food concentrations is especially acute for dreissenid mussels, despite their importance as invading species in fresh waters. We assessed the functional response of zebra mussels (Dreissena polymorpha) via feeding experiments and behavioral observations conducted at low food levels. Critically, food levels were chosen to be in the vicinity of minimum concentrations found in lakes with established D. polymorpha populations. Results of two feeding experiments show clear evidence of a Type III functional response for D. polymorpha feeding on Ankistrodesmus falcatus — clearance rate increased with increasing food concentration at low food levels. Mussels were always open and feeding during these experiments. An independent set of behavioral observations further showed that the fraction of mussels actively feeding (valves open, siphons extended) decreased as food concentrations decreased. We also measured somatic growth of juvenile mussels at varying levels of A. falcatus over 27 days and found that mussels were able to grow at food levels where Type III behavior was observed in the feeding experiments.

Growth and Respiration in Blue Mussels (Mytilusspp.) from Different Salinity Regimes

ABSTRACT Shell growth, weight-specific growth of the soft tissue, and oxygen consumption were measured in native blue mussels, Mytilus spp., fromdifferent locations inDenmark, covering a salinity range from ∼10 to ∼30. The greatest growth rates were observed in mussels growing at average salinities of 25.7 and 29.5, the lowest rates occurred at the location exhibiting the most fluctuating salinity regime over time, with an average 20.5. Individuals in waters with a salinity of 25.7 also displayed the greatest condition index of all locations (12.1mg/cm3, P < 0.05).Mussels from five of six locations displayed similar oxygen consumption rates (P ≤ 0.83) when standardized to weight (range, 0.78–0.88 mg O2/g/h. Of the salinities noted in the experiment, 25.7 appears to be the optimal salinity in terms of growth and condition, whereas strongly fluctuating salinity obviously involves reduced growth. At first glance, this study may appear to be just one among numerous attempts to describe the effect of salinity ...

The Effect of UV-C Exposure on Larval Survival of the Dreissenid Quagga Mussel.

The rapid spread of quagga mussels (Dreissena rostriformis bugensis) has lead to their invasion of Lake Mead, Nevada, the largest reservoir in North America and partially responsible for providing water to millions of people in the southwest. Current strategies for mitigating the growth and spread of quagga mussels primarily include physical and chemical means of removing adults within water treatment, delivery, and hydropower facilities. In the present study, germicidal ultraviolet light (UV-C) was used to target the larval stage of wild-caught quagga mussel. The lethal effect of UV-C was evaluated at four different doses, 0.0, 13.1, 26.2, and 79.6 mJ/cm2. Tested doses were determined based on results from preliminary trials. The results demonstrate that germicidal UV-C is effective in controlling the free-swimming life history stages of larval quagga mussels.

Growth, reproduction, and attachment of the golden mussel (Limnoperna fortunei) in water diversion projects

The golden mussel Limnoperna fortunei (Dunker, 1857) is a filter-feeding species of freshwater bivalve that is native to southern China. The species readily invades water transfer tunnels, causing considerable damage. The mussels typically attach to the walls of pipelines and gates, and are associated with serious biofouling. This may lead to increased flow resistance of the tunnels and to corrosion of their walls, and may threaten their operation. The mussels exhibit very high environmental adaptability and, once they become established in the water transfer works, they are impossible to eliminate. Therefore, prevention of the entry of golden mussels into the tunnels is considered to be the most efficient means of avoiding biofouling by this species. The main period of invasion corresponds with their reproductive season, which therefore forms the focus of prevention methods. Consequently, further study of reproduction of the golden mussel is essential. The process of attachment of golden mussels to material with a solid surface was studied experimentally in the Xizhijiang River, a tributary of the East River. It is the main water resource of the water transfer project supplying Shenzhen and Dongguan, southern China. Experiments were conducted from March 2010 to April 2011. Fourteen sets of materials were installed in the river to monitor attachment of the mussels. Shell-length frequency data of golden mussels attached on the monitoring materials were determined monthly and analyzed for identification of cohorts of individuals produced during successive reproductive seasons, and for measurement of their growth rates. The Windows version of FiSAT (FiSAT II), a software package developed specifically for the analysis of length-frequency data of aquatic biota, was applied in this study. The density of attachment of golden mussels to the monitoring materials was related to the water depth and to the orientation of the attachment surface. Clay and silt precipitation reduced the attachment density of the mussels. The attachment density on downward facing surfaces with lower sediment precipitation was much higher than the density on the upward facing surfaces with higher precipitation. A six-fold increase in precipitation of clay and silt was associated with a 90% decrease in attachment density. The analysis of monthly shell-length frequency indicated that the mussels produced three generations per year, each of which was associated with two reproductive peaks, resulting in six cohorts per year. The growth rates of the six cohorts differed and varied from month to month. Mean growth rates were in the range 0.4–3.5mm/month. The average growth rate was logarithmically related to the water temperature, total nitrogen and total phosphorus concentrations. Therefore, the time for the cohorts to reach maturity (shell length: 6–8mm) varied with these environmental parameters. The feasibility of preventing the attachment of golden mussels is discussed. Intensive prevention efforts should be performed during their peak reproductive seasons (March to May, June to September, and October to December). Clay or silt precipitation is recommended as a potential method for preventing the attachment of golden mussel to materials. However, because of the extended and frequent reproductive activities of golden mussels, preventing their invasion of water transfer tunnels remains a challenge; control strategies will need to be applied for long periods.

A floating cage system for rearing freshwater mussels Anodonta anatina and Unio mancus in Piedmont region (NW Italy)

This research represents the first attempt in Italy to develop a cage system for adult freshwater mussel stocking, for extensive farming, that was realized from 2003 to 2005 in NW Italy. Two autochthonous species of Italian freshwater mussel were used: Anodonta anatina and Unio mancus. 5133 mussels were collected and successively stocked in floating cages in 5 different sites in a lake. This study was planned in order to determine the effect of main rearing factors for potential farming: stocking density and cage position in the water column (depth). For each species, the effects of three rearing densities and two water depths were tested. Mussel growth was measured on a monthly basis in each experimental unit throughout the study. The survival rate at the end of the experiment for both species considered was 98.4%. U. mancus resulted to be more resistant to rearing conditions and during the summer the highest mortality was registered for A. anatina. Summer mortality was between 4.8% and 20.5%. Highest mortality in U. mancus was recorded in September 2004 at 1.5 m (3.6±2.4%), while the highest mortality for A. anatina was recorded in September 2003 as 13.3%±3.8% at a depth of 1.5 m. This research showed that cage stocking is a suitable method and the optimal position of cages is at the lake thermocline. The proposed species proved to be easily utilizable for future farming or bioremediation projects, and can readily be reared up to 135 kg m -3 .

Ocean Acidification Has Multiple Modes of Action on Bivalve Larvae.

Ocean acidification (OA) is altering the chemistry of the world’s oceans at rates unparalleled in the past roughly 1 million years. Understanding the impacts of this rapid change in baseline carbonate chemistry on marine organisms needs a precise, mechanistic understanding of physiological responses to carbonate chemistry. Recent experimental work has shown shell development and growth in some bivalve larvae, have direct sensitivities to calcium carbonate saturation state that is not modulated through organismal acid-base chemistry. To understand different modes of action of OA on bivalve larvae, we experimentally tested how pH, PCO2, and saturation state independently affect shell growth and development, respiration rate, and initiation of feeding in Mytilus californianus embryos and larvae. We found, as documented in other bivalve larvae, that shell development and growth were affected by aragonite saturation state, and not by pH or PCO2. Respiration rate was elevated under very low pH (~7.4) with no change between pH of ~ 8.3 to ~7.8. Initiation of feeding appeared to be most sensitive to PCO2, and possibly minor response to pH under elevated PCO2. Although different components of physiology responded to different carbonate system variables, the inability to normally develop a shell due to lower saturation state precludes pH or PCO2 effects later in the life history. However, saturation state effects during early shell development will carry-over to later stages, where pH or PCO2 effects can compound OA effects on bivalve larvae. Our findings suggest OA may be a multi-stressor unto itself. Shell development and growth of the native mussel, M. californianus, was indistinguishable from the Mediterranean mussel, Mytilus galloprovincialis, collected from the southern U.S. Pacific coast, an area not subjected to seasonal upwelling. The concordance in responses suggests a fundamental OA bottleneck during development of the first shell material affected only by saturation state.

Survival, growth and condition of freshwater mussels: effects of municipal wastewater effluent.

Freshwater mussels (Family Unionidae) are among the most imperiled group of organisms in the world, with nearly 65% of North American species considered endangered. Anthropogenic disturbances, including altered flow regimes, habitat alteration, and pollution, are the major driver of this group's decline. We investigated the effects of tertiary treated municipal wastewater effluent on survivorship, growth, and condition of freshwater mussels in experimental cages in a small Central Texas stream. We tested the effluent effects by measuring basic physical parameters of native three ridge mussels (Amblema plicata) and of non-native Asian clams (Corbicula fluminea), before and after 72-day exposure at four sites above and below a municipal wastewater treatment plant outfall. Survivorship and growth of the non-native Asian clams and growth and condition indices of the native three ridge mussels were significantly higher at the reference site above the outfall than in downstream sites. We attribute this reduction in fitness below the outfall to elevated nutrient and heavy metal concentrations, and the potential presence of other untested-for compounds commonly found in municipal effluent. These results, along with an absence of native mussels below the discharge, indicate a significant negative impact of wastewater effluent on both native and non-native mussels in the stream.