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Molluscs mineralize carbon as calcium carbonate in shells within a protein matrix that is a small portion of the total shell mass. In parts of Florida, the northern quahog Mercenaria mercenaria is cultured in mesh bags in shallow coastal marine habitats. These habitats were selected by the State of Florida for their pre-existing lack of large molluscan populations, so most of the shell material harvested by aquaculture operations would not otherwise exist. The carbonate content of shell material was quantified by coulometry, and shell production was estimated per harvested clam, and per unit area per year. The majority of the shell material harvested (about 91 %) was M. mercenaria, and the remainder came from other species of molluscs that grew in or on the mesh bags. Of the non-Mercenaria shell material, most (8.5% of total percentage) came from oysters (Crassostrea virginica and Ostrea stentina), and the rest from at least 37 other species of molluscs and other shelled taxa. Each harvested market-size clam represented approximately 2.93 g of mineralized carbon, including shell material that was not part of the marketed clams. Clam leases in full production produced about 1.0 * [10.sup.3] g of mineralized carbon per square meter per year, including nonclam shell material, and the Florida northern quahog industry produced about 534 metric tons of mineralized carbon in 2008. This mineralization resulted in an estimated atmospheric efflux of 374 tons of metabolic-independent carbon in the form of carbon dioxide, from the Florida northern quahog industry in 2008. KEY WORDS: molluscan shell, carbon mineralization, nitrogen sequestration, calcium carbonate, bivalve mollusc, Mercenaria, Crassostrea, Ostrea, INTRODUCTION Carbon is mineralized as calcium carbonate by corals, molluscs, and other organisms with calcareous skeletons; some researchers refer to this as calcimass in quantitative studies (Beukema 1980, Munari et [...]

ABSTRACT The green mussel Perna viridis (Linnaeus 1758), a native of the Indo-Pacific, has been introduced to the Atlantic basin and Caribbean Sea. It was reported first in Cienfuegos Bay, [...]

ABSTRACT Aquacultured hard clams (Mercenaria mercenaria) from Florida were examined for Perkinsus spp. using culture in Rays Fluid Thyioglycollate Medium (RFTM) and PCR. Clams were negative for P. marinus-specific PCR, [...]

ABSTRACT The tropical Asian green mussel, Perna viridis (Bivalvia: Mytilidae) is a recent invader in the Caribbean Basin, including the subtropical southeastern United States. In this study we examined the [...]

ABSTRACT Histologic examination of the normative green mussel, Perna viridis, and the native scorched mussel, Brachidontes exustus, at three locations in Tampa Bay, Florida, indicated that cycles of gametogenesis and [...]

ABSTRACT Sudden salinity drops in Gulf Coast clam growing areas in Florida have been suggested as a cause of seed (juvenile) clam mortality. Laboratory experiments were used to assess short-term [...]

Bivalve molluscs can have profound effects on the ecosystems in which they live. Zebra mussels (Dreissena polymorpha) invaded North America in the 1980% and have severely lowered phytoplankton stocks and increased water clarity. Their invasion of the Hudson River in 1989 has dramatically changed the phytoplankton species composition and total abundance: dominant blue-greens have disappeared, diatoms now dominate, and phytoplankton standing stocks have declined profoundly, while turbidity has remained high. We examined the feeding rate and feeding selectivity of zebra mussels using standard techniques as well as flow cytometry. We have found that i) zebra mussels prefer the formerly dominant blue-green species that has disappeared from the river, ii) zebra mussels feed selectively on blue-green algae and smaller greens, generally excluding large greens and diatoms, and iii) biodeposits (feces and pseudofeces) of inert particles (clay) and diatoms are easily resuspended. Our results indicate that the interaction of selective feeding by zebra mussels and the resuspension of biodeposits by tidal mixing may explain the differential decline in phytoplankton groups that has occurred in the Hudson River.

The apple snail Pomacea maculata is a recent introduction to Florida from its native range in South America. Little is known about the growth characteristics of apple snails. We measured δ18Oaragonite values along the shell growth axis of the non-native, aquatic pulmonate gastropod, Pomacea maculata, to determine its life span and seasonal growth pattern in Florida. Age, growth rate, and season of growth of P. maculata were determined from seasonal temperature fluctuations, inferred from δ18O values measured on aragonite drilled along the shell whorl. Eight of the 22 P. maculata lived less than one year, ten slightly longer than one year, and one into its third year. Three snails yielded indeterminate results. Snails from lakes Tulane and Verona deposited the majority of carbonate during late fall/early winter, whereas growth in Newnans Lake was divided across the seasons. Among specimens taken alive, and for which time of death was known, there were offsets along the shell margin with respect to δ18O values predicted from δ18Olake-water and temperature. The δ18Oaragonite of snails raised in temperature-controlled settings, however, was in close agreement with calculated empirical values. Isotopic offsets along the growth margin are probably a consequence of diminished carbonate deposition with increased specimen age. [ABSTRACT FROM AUTHOR]

The Suwannee River watershed is one of the least developed in the eastern United States, but with increasing urbanization it is facing potential long-term alterations in freshwater flow to its estuary in the Gulf of Mexico. The purpose of this study was to develop biological indicators of oyster reef state along a natural salinity gradient in the Suwannee River estuary in order to allow the rapid assessment of the effect of changing freshwater input to this system. Percent cover and density of three size classes of living oysters, as well as the abundance of several predominant reef-associated invertebrates, were measured along a broad salinity gradient in the estuary and were correlated with salinity estimates from a long-term database for the preceding 12-24 mo. All eastern oyster, Crassostrea virginica, parameters (percent cover and density of three size classes) were significantly and negatively related to salinity. Data from samples collected near the lower intertidal were more closely dependent upon salinity than were samples from the higher intertidal at the same sites. Salinity differences were most closely reflected in differences in total oyster cover. This relationship corresponded with a general decline in oyster habitat with increasing distance from the mouth of the Suwannee River. Species richness was significantly and positively correlated with all C. virginica parameters (percent cover and density of three size classes), but the relationship explained only about half the variability. Density data of the hooked mussel, Ischadium recurvum, and a mud crab, Eurypanopeus depressus, were positively and strongly correlated with C. virginica parameters, likely reflecting the abundance of habitat provided by C. virginica shells. All of the biological indicators measured responded similarly along the salinity gradient, indicating they provide reliable indices of the effect of changing salinities in the Suwannee River estuary over the previous 1 or 2 yr. Some areas of positive relief defined as reefs 30 years ago are no longer oyster habitat, suggesting an ongoing decline, but nearshore C. virginica were abundant. [ABSTRACT FROM AUTHOR]

The excessive number of terms associated with invasive species, and their often incorrect usage, hinders stakeholder education about the threats of invasive species. Here we introduce seven terms (native, nonnative, introduced, established, invasive, nuisance, and range change) that are applicable across invasive taxa, understandable, typically interpreted correctly, and useful for describing most situations regarding invasive species. We also list six terms to avoid (native invasive, invasive exotic, invasive weed, alien, foreign, and nonindigenous) that create confusion via their misuse and misinterpretation. The terms we propose will increase understanding, thereby promoting behavior changes aimed at limiting the negative impacts of invasive species. [ABSTRACT FROM AUTHOR]