ESTIMATIVAS DE PRODUÇÃO SECUNDÁRIA NA COSTA PORTUGUESA UTILIZANDO MÉTODOS DE DETECÇÃO REMOTA

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Reproduction and respiration of a climate change indicator species: effect of temperature and variable food in the copepod Centropages chierchiae

Publication . Cruz, Joana; Garrido, Susana; Pimentel, Marta S.; Rosa, Rui; Santos, A. Miguel P.; Re, Pedro

The abundance of the calanoid copepod Centropages chierchiae has increased at the northern limits of its distribution in recent decades, mainly due to oceanic climate forcing, suggesting this as a key species in monitoring climate change. Laboratory experiments were conducted to study the combined effect of temperature, food type and concentration on the egg production rate (EPR) and hatching success (HS) of C. chierchiae. Females were fed on two monoalgal diets (Gymnodinium sp. and Phaeodactylum tricornutum) at two food concentrations and at three different temperatures (13, 19, 24C). Respiration rates of both genders were measured at four different temperatures (8, 13, 19, 24C). EPR was significantly different between temperatures and food concentrations, the maximum EPR being attained when the copepods were exposed to high food levels and at 19C. Prey type significantly influenced EPR; feeding on P. tricornutum resulted in higher egg production than Gymnodinium sp. HS was significantly lower at 13C than at 19 and 24C and higher with Gymnodinium sp. Respiration rates were sex independent and increased exponentially with temperature. To maintain basal metabolism, the minimum food intake of P. tricornutum ranged between 0.4 and 1.8 g C and for Gymnodinium sp. between 0.03 and 0.13 g C. Food intake was always higher than the metabolic demands, except for the highest temperature tested (24C). The present results confirm the sensitivity of C. chierchiae to temperature variations and may help in understanding the successful expansion of its distribution towards northern latitudes.

2013-10Journal article

Open access

RNA:DNA ratios as a proxy of egg production rates of Acartia

Publication . Cruz, Joana; Alexandra Teodosio Chicharo, Maria; Ben-Hamadou, Radhouane; Manuel Zambujal Chicharo, Luis; Garrido, Susana; Re, Pedro; Santos, A.M.P.

Estimates of copepod secondary production are of great importance to infer the global organic matter fluxes in aquatic ecosystems and species-specific responses of zooplankton to hydrologic variability. However, there is still no routine method to determine copepods secondary production in order to eliminate time consuming experimental analyses. Therefore, we determined whether there is a correlation between Egg Production Rates (EPR) and RNA:DNA ratios of Acartia species, by measuring their seasonal and spatial variability and the influence of environmental factors for Acartia sp. collected in the Guadiana river estuary. EPR of Acartia tonsa was positively related with chlorophyll a concentration, freshwater inflow and biomass of dinoflagellates, while Acartia clausi was only related to dinoflagellates. Dinoflagellates seem to be the optimal food item influencing the reproduction of both Acartia species in the studied area. The biochemical index RNA:DNA was positively related to EPR, indicating that it is a good proxy of copepod production and a promising method to use in the future to estimate secondary production. (C) 2017 Elsevier Ltd. All rights reserved.

2017-03Journal article

Open access

Plankton community and copepod production in a temperate coastal lagoon: what is changing in a short temporal scale?

Publication . Cruz, Joana; Teodosio, Maria; Garrido, Susana; Ben-Hamadou, Radhouane; Chicharo, Luis; Ré, Pedro; Santos, A.M.P.

Coastal lagoons are often exposed to intense short-term environmental changes and strong anthropogenic pressures influencing zooplanktonic communities and production. However, most works focus on long-term temporal scales using monthly or seasonal sampling strategies. The present study analysed the structure of the mesozooplanktonic assemblages, the production (egg production rates) and physiological condition (RNA:DNA ratio) of the copepod Acartia clausi in a temperate coastal lagoon (Ria Formosa) during the summer, using an intensive sampling approach. Salinity was the main factor affecting the short-term variability of mesozooplankton composition, followed by tidal phase (ebb tides) and semilunar cycle (spring tides). There was a positive relationship between the abundance of Appendicularia and the cladoceran Penilia avirostris with the toxic dinoflagellate Gymnodinium catenatum, suggesting no deleterious effects. The egg production rate of A. clausi was influenced by salinity and ammonia concentration, with a positive correlation between the egg productivity and the macronutrient, showing a possible adaptation of this calanoid species. The RNA:DNA index was positively related to egg production rate, suggesting that it is a good proxy for the reproductive output of copepods, even in short-term periods. This study shows that different timescales need to be included in regular monitoring of planktonic assemblages in coastal lagoons in order to understand the influence of environmental and anthropogenic variables on marine organisms.

2020Journal article

Open access