The harmful dinoflagellate Prorocentrum minimum has different effects upon various species of grazing bivalves, and these effects also vary with life-history stage.Possible effects of this dinoflagellate upon mussels have not been reported; therefore, experiments exposing adult blue mussels, Mytilus edulis, to P. minimum were conducted. Mussels were exposed to cultures of toxic P. minimum or benign Rhodomonas sp. in glass aquaria. After a short period of acclimation, samples were collected on day 0 (before the exposure) and after 3, 6, and 9 days of continuousexposure experiment. Hemolymph was extracted for flow-cytometric analyses of hemocyte, immune-response functions, and soft tissues were excised for histopathology.Mussels responded to P. minimum exposure with diapedesis of hemocytes into the intestine, presumably to isolate P. minimum cells within the gut, thereby minimizing damage to other tissues. This immune response appeared to have been sustained throughout the 9-day exposure period, as circulating hemocytes retained hematological and functional properties. Bacteria proliferated in the intestines of the P. minimumexposed mussels. Hemocytes within the intestine appeared to be either overwhelmed by the large number of bacteria or fully occupied in the encapsulating response to P. minimum cells; when hemocytes reached the intestine lumina, they underwent apoptosis and bacterial degradation. This experiment demonstrated that M. edulis is affected by ingestion of toxic P. minimum; however, the specific responses observed in the blue mussel differed from those reported for other bivalve species. This finding highlights the need to study effects of HABs on different bivalve species, rather than inferring that results from one species reflect the exposure responses of all bivalves.

The harmful dinoflagellate Prorocentrum minimum has different effects upon various species of grazing bivalves, and these effects also vary with life-history stage.Possible effects of this dinoflagellate upon mussels have not been reported; therefore, experiments exposing adult blue mussels, Mytilus edulis, to P. minimum were conducted. Mussels were exposed to cultures of toxic P. minimum or benign Rhodomonas sp. in glass aquaria. After a short period of acclimation, samples were collected on day 0 (before the exposure) and after 3, 6, and 9 days of continuousexposure experiment. Hemolymph was extracted for flow-cytometric analyses of hemocyte, immune-response functions, and soft tissues were excised for histopathology.Mussels responded to P. minimum exposure with diapedesis of hemocytes into the intestine, presumably to isolate P. minimum cells within the gut, thereby minimizing damage to other tissues. This immune response appeared to have been sustained throughout the 9-day exposure period, as circulating hemocytes retained hematological and functional properties. Bacteria proliferated in the intestines of the P. minimumexposed mussels. Hemocytes within the intestine appeared to be either overwhelmed by the large number of bacteria or fully occupied in the encapsulating response to P. minimum cells; when hemocytes reached the intestine lumina, they underwent apoptosis and bacterial degradation. This experiment demonstrated that M. edulis is affected by ingestion of toxic P. minimum; however, the specific responses observed in the blue mussel differed from those reported for other bivalve species. This finding highlights the need to study effects of HABs on different bivalve species, rather than inferring that results from one species reflect the exposure responses of all bivalves.

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41Land-based management has reduced nutrient discharges, however, many coastal waterbodies waterbodies without circulation models. The value of removed nitrogen was estimated using

Eastern oysters Crassostrea virginica and hard clams Mercenaria mercenaria are key organisms for both the ecosystem services they provide and for their commercial value, but their populations have declined greatly worldwide. In an attempt to understand the interaction between bivalve physiology and environmental conditions, filter-feeding assays were carried out in a shallow estuary, the Indian River Lagoon (IRL; Florida, USA). The feeding behavior of the bivalves was studied using in situ filter-feeding devices and the biodeposition method in the 3 basins of the IRL during March and August 2015. Water characteristics (temperature, salinity, dissolved oxygen, chl a, and total, organic, and inorganic particulates) were related to possible changes in the feeding physiology of the bivalves. Oysters had higher clearance rates, filtration rates, and rejection than clams. The high rejection of inorganic matter allowed oysters to increase the organic matter ingested, leading to high absorption efficiencies. In contrast, because clam rejection was low regardless of elevated levels of inorganic matter, their absorption efficiency only increased with higher organic matter content. Both species preferred higher salinities, and the amount of organic matter in the water had a negative relationship with some feeding parameters (filtration rate for both species, and rejection for oysters). Acute environ mental change brought about by a brown tide (caused by the alga Aureoumbra lagunensis) also affected these 2 bivalve species differently, supporting the hypothesis that oysters and clams have different physiological capabilities that drive their ability to survive in dynamic estuarine ecosystems.KEY WORDS: Indian River Lagoon · Brown tide · Aureoumbra lagunensis · Seston · Clearance rate · Bivalves Resale or republication not permitted without written consent of the publisher Editorial responsibility: Romuald Lipcius,

The Atlantic ribbed mussel, Geukensia demissa, is found in salt marshes along the North American Atlantic Coast. As a first step to study the possibility of future cultivation and harvest of ribbed mussels for nutrient removal from eutrophic urban environments, the feeding behavior of ribbed mussels in situ was studied from July to October 2011. Two locations approximately 80 km apart were used as study sites: Milford Harbor (Connecticut; 41°12′42.46″N, 73°3′7.75″W) and Hunts Point (Bronx, New York; 40°48′5.99″N, 73°52′17.76″W). Total particulate matter was higher at Hunts Point than at Milford Harbor, but the organic content was higher at Milford than at Hunts Point. The relatively low quantity of organic content in Hunts Point seston resulted in a much higher production of pseudofeces by mussels. Mussel clearance and absorption rates were higher at Milford Harbor than at Hunts Point. Nevertheless, mussels at both sites had the same absorption efficiency, suggesting that mussels are able to adapt to conditions at both locations. Ribbed mussels decreased clearance rate when the seston quantity was high at both sites. At Hunts Point, ribbed mussels increased the gut transit time of ingested particles when the amount of inorganic particulates in the water increased. This study does not quantify nutrient removal capacity of G. demissa; however, the environmental tolerance demonstrated here, and current lack of commercial harvest, suggests that this species may be a good candidate for nutrient bioextraction in highly impacted urban environments.

The effects of exposure to the type species for Karlodinium veneficum (PLY # 103) on immune function and histopathology in the blue mussel Mytilus edulis were investigated. Mussels from Whitsand Bay, Cornwall (UK) were exposed to K. veneficum (PLY # 103) for 3 and 6 days. Assays for immune function included total and differential cells counts, phagocytosis and release of extra cellular reactive oxygen species. Histology was carried out on digestive gland and mantle tissues. The toxin cell quota for K. veneficum (PLY #103) was measured by liquid chromatography-mass spectrometry detecting two separable toxins KvTx1 (11.6 ± 5.4 ng/ml) and KvTx2 (47.7 ± 4.2 ng/ml). There were significant effects of K. veneficum exposure with increasing phagocytosis and release of reactive oxygen species following 6 days exposure. There were no significant effects on total cell counts. However, differential cell counts did show significant effects after 3 days exposure to the toxic alga. All mussels produced faeces but not pseudofaeces indicating that algae were not rejected prior to ingestion.Digestive glands showed ingestion of the algae and hemocyte infiltration after 3 days of exposure, whereas mantle tissue did not show differences between treatments. As the effects of K. veneficum were not observed in the mantle tissue it can be hypothesized that the algal concentration was not high enough, or exposure long enough, to affect all the tissues. Despite being in culture for more than 50 years the original K. veneficum isolate obtained by Mary Parke still showed toxic effects on mussels.