Combined effects of a parasite, QPX, and the harmful-alga, Prorocentrum minimum on northern quahogs, Mercenaria mercenaria

Northern quahogs, Mercenaria mercenaria (L.), frequently are infected with the parasite Quahog Parasite Unknown (QPX, Labyrintohomorpha, Thraustochytriales), which can cause morbidity and mortality of the quahogs. Possible interactions between this parasitic disease and exposure to the harmful dinoflagellate Prorocentrum minimum in M. mercenaria were studied experimentally. Quahogs from Massachusetts with variable intensity of QPX infection were exposed, under controlled laboratory conditions, to cultured P. minimum added to the natural plankton at a cell density equivalent to a natural bloom. After 5 days of exposure, individual clams were diagnosed histologically to assess prevalence and intensity of parasitic infection, as well as other pathological conditions. Further, cellular defense status of clams was evaluated by analyzing hemocyte parameters (morphological and functional) using flow-cytometry. Exposure of quahogs to P. minimum resulted in: a lower percentage of phagocytic hemocytes, higher production of reactive oxygen species (ROS), larger hemocyte size, more-numerous hemocytic aggregates, and increased numbers of hemocytes in gills accompanied by vacuolation and hyperplasia of the water-tubular epithelial cells of the gills. Quahogs had a low prevalence of QPX; by chance, the parasite was present only in quahogs exposed to P. minimum. Thus, the effect of QPX alone on the hemocyte parameters of quahogs could not be assessed in this experiment, but it was possible to assess different responses of infected versus non-infected quahogs to P. minimum. QPX-infected quahogs exposed to P. minimum had repressed percentage of phagocytic hemocytes, consistent with immuno-modulating effect of P. minimum upon several molluscan species, as well as smaller hemocytes and increased hemocyte infiltration throughout the soft tissues. This experiment demonstrates the importance of considering interactive effects of different factors on the immunology and histopathology of bivalve shellfish, and highlights the importance of considering the presence of parasites when bivalves are subjected to harmful-algal blooms

GROWTH CHARACTERISTICS OF NEWLY ISOLATED INDONESIAN MICROALGAE UNDER DIFFERENT SALINITY

The aim of this study was to investigate the growth characteristics of microalgae strains isolated from Kendari Bay and the Wanggu River estuary, Indonesia. The growth of the isolates, denoted as Kb1-2, Kb1-3, Kb1-5, and Kb2-6, were evaluated under controlled conditions. A batch culture experiment of these strains except Kb2-6 was conducted for 15 days under salinity levels of 20, 25, 30 and 35 gL-1. Tetraselmis chui, Tisochrysis lutea and Chaetocero sneogracile were also culture and used as the growth references. Cell density was measured every day and cell size was measured from 50 live cells during the logarithmic phase. The cell sizes of three of the four Indonesian microalgae ranged from 1.2-11.8 µm, considered suitable for shrimp larvae. The Indonesian strains started the logarithmic phase of growth at all salinities tested from day 0 to day 3 after inoculation except for Kb1-3 that started the phase after a 3-day lag. Increased cell density over the culture period and division rate of Indonesian microalgae during the logarithmic phase of growth were similar at all salinities tested and similar to T. chui, Ti. lutea and C. neogracile. However, the final biomasses after 15 days of culture of all microalgal strains were affected by culture salinities tested. Indonesian microalgal strains showed similar dry weight and ash free dry weight to smaller-cell strains, Ti. lutea and C. neogracile. Indonesian strains (other than Kb2-6) are suggested as suitable live food candidates for mass culture in shrimp hatcheries based on their cell size, ability to survive long culture periods, and wide salinity tolerance

Salinity Effects on Growth and Nutritional Content of Newly Isolated Microalgal with Potential Use in The Shrimp-Hatcheries

A two-week batch experiment was conducted on three newly isolated Indonesian microalgal strains (Kb1-2 identified as Chaetoceros sp., Kb1-3 and Kb1-5) and Tisochrysis lutea to determine salinity effects upon the growth, proximate composition and ω-3, eicosapentaenoic acidand docosahexaenoic acid, (EPA and DHA) and ω-6 (arachidonic acid /ARA) fatty acids. Salinity within each strain growth of all microalgae tested. The highest cell densities were observed in Indonesian strains, Kb1-3 on day 8 at 25 psu and Kb1-5 on day 10 at 35 psu. Salinity significantly affected the lipid, protein and carbohydrate content in all microalgae cultured. The highest total lipid content was found in T. lutea cultured at 30 psu (28.3 %) followed by Kb1-2 cultured at 20 psu (25.0 %) and T. lutea at 35 psu (24.8 %). Kb1-3 produced highest protein when cultured at 20 and 25 psu, decreasing at higher salinities of 30 and 35 psu, 44.7 and 39.2 % to 31.5 and 32.6 %, respectively, similar to T. lutea. Kb1-5 had higher protein at both 25 and 35 psu but showed lower protein levels at 20 and 30 psu. Indonesian strains showed almost a similar content of carbohydrate across culture salinities similar to T. lutea. Although all Indonesian microalgae contained important ω-3 (EPA and DHA) and ω-6 (ARA) fatty acids, concentrations were low in comparison to T. lutea. All Indonesian microalgal strains also contained the dicarboxylic acid (DCA), phthalic acid, which was not present in T. lutea

Effects of CO\u3csub\u3e2\u3c/sub\u3e on Growth Rate, C:N:P, and Fatty Acid Composition of Seven Marine Phytoplankton Species

Carbon dioxide (CO2) is the primary substrate for photosynthesis by the phytoplankton that form the base of the marine food web and mediate biogeochemical cycling of C and nutrient elements. Specific growth rate and elemental composition (C:N:P) were characterized for 7 cosmopolitan coastal and oceanic phytoplankton species (5 diatoms and 2 chlorophytes) using low density, nutrient-replete, semi-continuous culture experiments in which CO2 was manipulated to 4 levels ranging from post-bloom/glacial maxima (ppm) to geological maxima levels (\u3e2900 ppm). Specific growth rates at high CO2 were from 19 to 60% higher than in low CO2 treatments in 4 species and 44% lower in 1 species; there was no significant change in 2 species. Higher CO2 availability also resulted in elevated C:P and N:P molar ratios in Thalassiosira pseudonana (~60 to 90% higher), lower C:P and N:P molar ratios in 3 species (~20 to 50% lower), and no change in 3 species. Carbonate system-driven changes in growth rate did not necessarily result in changes in elemental composition, or vice versa. In a subset of 4 species for which fatty acid composition was examined, elevated CO2 did not affect the contribution of polyunsaturated fatty acids to total fatty acids significantly. These species show relatively little sensitivity between present day CO2 and predicted ocean acidification scenarios (year 2100). The results, however, demonstrate that CO2 availability at environmentally and geologically relevant scales can result in large changes in phytoplankton physiology, with potentially large feedbacks to ocean biogeochemical cycles and ecosystem structure

Culture optimization for the emergent zooplanktonic model organism Oikopleura dioica

The pan-global marine appendicularian, Oikopleura dioica, shows considerable promise as a candidate model organism for cross-disciplinary research ranging from chordate genetics and evolution to molecular ecology research. This urochordate, has a simplified anatomical organization, remains transparent throughout an exceptionally short life cycle of less than 1 week and exhibits high fecundity. At 70 Mb, the compact, sequenced genome ranks among the smallest known metazoan genomes, with both gene regulatory and intronic regions highly reduced in size. The organism occupies an important trophic role in marine ecosystems and is a significant contributor to global vertical carbon flux. Among the short list of bona fide biological model organisms, all share the property that they are amenable to long-term maintenance in laboratory cultures. Here, we tested diet regimes, spawn densities and dilutions and seawater treatment, leading to optimization of a detailed culture protocol that permits sustainable long-term maintenance of O. dioica, allowing continuous, uninterrupted production of source material for experimentation. The culture protocol can be quickly adapted in both coastal and inland laboratories and should promote rapid development of the many original research perspectives the animal offers

Attraction and repulsion of mobile wild organisms to finfish and shellfish aquaculture: a review

Knowledge of aquaculture–environment interactions is essential for the development of a sustainable aquaculture industry and efficient marine spatial planning. The effects of fish and shellfish farming on sessile wild populations, particularly infauna, have been studied intensively. Mobile fauna, including crustaceans, fish, birds and marine mammals, also interact with aquaculture operations, but the interactions are more complex and these animals may be attracted to (attraction) or show an aversion to (repulsion) farm operations with various degrees of effects. This review outlines the main mechanisms and effects of attraction and repulsion of wild animals to/from marine finfish cage and bivalve aquaculture, with a focus on effects on fisheries-related species. Effects considered in this review include those related to the provision of physical structure (farm infrastructure acting as fish aggregating devices (FADs) or artificial reefs (ARs), the provision of food (e.g. farmed animals, waste feed and faeces, fouling organisms associated with farm structures) and some farm activities (e.g. boating, cleaning). The reviews show that the distribution of mobile organisms associated with farming structures varies over various spatial (vertical and horizontal) and temporal scales (season, feeding time, day/night period). Attraction/repulsion mechanisms have a variety of direct and indirect effects on wild organisms at the level of individuals and populations and may have implication for the management of fisheries species and the ecosystem in the context of marine spatial planning. This review revealed considerable uncertainties regarding the long-term and ecosystem-wide consequences of these interactions. The use of modelling may help better understand consequences, but long-term studies are necessary to better elucidate effects

First Evidence of Immunomodulation in Bivalves under Seawater Acidification and Increased Temperature

Water acidification, temperature increases and changes in seawater salinity are predicted to occur in the near future. In such a global climate change (GCC) scenario, there is growing concern for the health status of both wild and farmed organisms. Bivalve molluscs, an important component of coastal marine ecosystems, are at risk. At the immunological level, the ability of an organism to maintain its immunosurveillance unaltered under adverse environmental conditions may enhance its survival capability. To our knowledge, only a few studies have investigated the effects of changing environmental parameters (as predicted in a GCC scenario) on the immune responses of bivalves. In the present study, the effects of both decreased pH values and increased temperature on the important immune parameters of two bivalve species were evaluated for the first time. The clam Chamelea gallina and the mussel Mytilus galloprovincialis, widespread along the coast of the Northwestern Adriatic Sea, were chosen as model organisms. Bivalves were exposed for 7 days to three pH values (8.1, 7.7 and 7.4) at two temperatures (22 and 28°C). Three independent experiments were carried out at salinities of 28, 34 and 40 PSU. The total haemocyte count, Neutral Red uptake, haemolymph lysozyme activity and total protein levels were measured. The results obtained demonstrated that tested experimental conditions affected significantly most of the immune parameters measured in bivalves, even if the variation pattern of haemocyte responses was not always linear. Between the two species, C. gallina appeared more vulnerable to changing pH and temperature than M. galloprovincialis. Overall, this study demonstrated that climate changes can strongly affect haemocyte functionality in bivalves. However, further studies are needed to clarify better the mechanisms of action of changing environmental parameters, both individually and in combination, on bivalve haemocytes