Filtration rate, assimilation and assimilation efficiency inCrassostrea virginica(Gmelin) fed withTetraselmis suecicaunder cadmium exposure

Abstract

Crassostrea virginica is an epibentic filter-feeding bivalve of economical importance in coastal lagoons of the Gulf of Mexico, locations with increasing inputs of heavy metals such as cadmium that have become environmental stressors. In this study, feeding and assimilation of the species were evaluated as physiological indicators of cadmium exposure. For this purpose, the filtration rate (FR), food assimilation (A) and assimilation efficiency (AE) of oysters from the Mandinga Lagoon, Veracruz, Mexico, were examined under sublethal and environmentally realistic cadmium concentrations (95 and 170 micro gCd L(-1)). Semi-static, 12-day bioassays were conducted with organisms placed into individual chambers and fed daily with Tetraselmis suecica. FR was calculated by measuring the depletion in algal density. Caloric contents of food and feces produced were also obtained. Condition Index (CI) and morphometric parameters were evaluated at the beginning and at the end of the assay. Total cadmium concentrations were quantified in water and tissue, and the metal bioconcentration factor (BCF) was calculated. Cadmium exposure significantly reduced FR in oysters (mean value: 0.64 L h(-1) and 0.44 L h(-1)) from control values (1.17 L h(-1)). Extreme values among results demonstrate the existence of a high FR (over 4 L h(-1)) mainly in control oysters, and this was associated with a better physiological condition; a low FR (under 2.5 L h(-1)) indicated metabolic stress as a consequence of Cd exposure. A and AE were significantly modified due to cadmium external levels, and time of exposure. FR and A were linearly related, and both decreased as metal BCF increased. Cadmium bioaccumulation was linearly related with external metal levels. The physiological deterioration of native C. virginica from Mandinga Lagoon was reflected in the alteration of FR, A and AE due to cadmium exposure in concentrations considered sublethal, lowering the feeding and assimilation capability of the organisms. The weight loss and mortality recorded in the oysters exposed to the highest metal concentration, was the final consequence of the overall adverse effect of cadmium exposure.

Bioremediation of Metal-Rich Effluents: Could the Invasive Bivalve Corbicula fluminea Work as a Biofilter?

“…However, further studies are still necessary to assess the suitability of such a sequential multistage assembly. High levels of metal in water may impact the clam's physiology, for example, by damaging the gill structure (Barrera‐Escorcia et al, 2010), and may change the metals’ physiological handling during accumulation, sequestration, distribution, and elimination (Wang and Rainbow, 2008). Additionally, if clam regeneration is necessary, the assessment of the most adequate regeneration periods for each clam batch, as well as the related methods to easily and efficiently discard contaminated clams that die or are no longer effective in bioremediation (Baudrimont et al, 1997) should be the next steps to address as actual implementation of the system is considered.…”

A review of existing eastern oyster filtration rate models

“…Filtration rate range * Study oyster size ** Maximum rate a Measurement method Experimental condition Barrera-Escorcia et al (2012) 0.02-0.07 1.38 0.08 Change in algal cells using a Nebauer chamber NA Comeau et al (2008) 0.01-0.12 1.1 0.12 Change in particles using a Coulter counter T 0-9 • C Gerritsen et al (1994) 0.24 1 0.24 Literature search NA Grizzle et al (2008) 0-0.48 0.19 0.30 In situ chlorophyll-a changes NA Langefoss and Maurer (1975) 0.13-0.40 0.21-0.42 0.28 Change in algal cells using a Coulter counter Food content Loosanoff (1958) 0-0.39 1.99 0.47 Kymograph T 2-38 • C Loosanoff and Nomejko (1946) 0.32-0.46 1.87 0.54 Dockside kymograph Tide/light Newell et al (2005) 0-0.46 1 0.46 Interpretation of Jordan (1987) NA Newell and Koch (2004) 0.04-0.46 1 0.46 Change in light measurements T 15-25 • C Palmer (1980) 0-0.26 1 0.26 Change in algal cells using a Coulter counter Light and food type Riisgard (1988) 0.33-0.69 0.06-0.99 0.33 Change in particles using a Coulter counter NA * m 3 g −1 oyster C day −1 . ** g DW.…”