Short-term UVR exposure affects feeding in nauplii of copepods from coastal waters off Patagonia (Argentina)

M.L. SPINELLI; R. J. GONÇALVES; F. L. CAPITANIO

Mar del Plata

Conferencia; CERF 2012. The Changing Coastal and Estuarine Environment: A Comparative Approach; 2012

Coastal & Estuarine Research Federation

UVR (280-400 nm) may negatively affect how zooplankton capture, ingest, digest, and assimilate their food. Zooplankton may obtain protection by bioaccumulation of UV-absorbing compounds from their food preys. The aim of this study was to evaluate whether the ingestion rate of copepod nauplii fed on Heterocapsa sp (H-) and Heterocapsa sp rich in UV-absorbing compounds (H+) are affected by UVR and subsequent light regime. Nauplii were collected in surface waters and fed (?Feeding 1?), for 24 h at in situ temperature, on either (H-) or (H+). Then they were exposed to UVR and PAR (400-700 nm) treatments for 4 h (irradiances of 0.7, 48 and 164 W m-2 for UVB, UVA and PAR, respectively). After the exposure, nauplii were incubated either in dark or under PAR (photoperiod) the same food as ?feeding 1? during 24 h (?Feeding 2?). Samples were fixed with Lugol for cell counting to estimate the ingestion rate (cells number/ nauplii/ h). In Feeding 1, ingestion rates were similar with both diets (367 and 474 cells/nauplii /h respectively; P>0.05). In Feeding 2, with both diets, nauplii receiving dark UVR treatment did not feed, and in photoperiod their ingestion rate was significantly lower in those exposed to UVR than in the PAR treatment (p <0.05). We observed that the ingestion rate decreased in nauplii treated with UVR. Moreover, the results suggest that the photorepair may be an important strategy in this group of larvae. These results are important considering that 1) the carbon flow from primary producers to primary consumers is greatly affected by the ingestion of food by herbivorous zooplankton and 2) the feeding and survival of nauplii larvae is a fundamental aspect for the copepod populations; therefore a UVR-induced decrease in the ingestion rate of nauplii may affect the amount of carbon and energy available to other trophic levels.Heterocapsa sp (H-) and Heterocapsa sp rich in UV-absorbing compounds (H+) are affected by UVR and subsequent light regime. Nauplii were collected in surface waters and fed (?Feeding 1?), for 24 h at in situ temperature, on either (H-) or (H+). Then they were exposed to UVR and PAR (400-700 nm) treatments for 4 h (irradiances of 0.7, 48 and 164 W m-2 for UVB, UVA and PAR, respectively). After the exposure, nauplii were incubated either in dark or under PAR (photoperiod) the same food as ?feeding 1? during 24 h (?Feeding 2?). Samples were fixed with Lugol for cell counting to estimate the ingestion rate (cells number/ nauplii/ h). In Feeding 1, ingestion rates were similar with both diets (367 and 474 cells/nauplii /h respectively; P>0.05). In Feeding 2, with both diets, nauplii receiving dark UVR treatment did not feed, and in photoperiod their ingestion rate was significantly lower in those exposed to UVR than in the PAR treatment (p <0.05). We observed that the ingestion rate decreased in nauplii treated with UVR. Moreover, the results suggest that the photorepair may be an important strategy in this group of larvae. These results are important considering that 1) the carbon flow from primary producers to primary consumers is greatly affected by the ingestion of food by herbivorous zooplankton and 2) the feeding and survival of nauplii larvae is a fundamental aspect for the copepod populations; therefore a UVR-induced decrease in the ingestion rate of nauplii may affect the amount of carbon and energy available to other trophic levels.