Vulnerability of Patagonian planktonic copepods to fluctuations in temperature and UV radiation

Abstract

The aim of this investigation is to address the impact of fluctuations in temperature and ultraviolet radiation (UVR) on three species of South American copepods, Boeckella antiqua, B. gracilis and B. brevicaudata. These copepods are cold stenotherm and occur in high latitude lakes of South America and in mountain lakes in the Andes. The forecast scenarios for climate change in southern South America anticipate raising temperature and UVR levels. These changes may have the potential to impact high altitude and latitude ecosystems, including lakes and their cold adapted biota, such as those in Patagonia. Laboratory experiments, consisting of 10 day and 2 day incubations, were set up to analyse copepod mortahty in relation with: (i) temperature, and (ii) the combined effect of temperature (5, 8, 12, 16, 20°C) and 194 and 324 J m^^). The results obtained showed up that temperature is a limiting factor for B. brevicaudata that did not survive above 12°C. B. antiqua and B. gracilis withstood the temperature range although their mortality was higher at 12-16°C. The survivorship of these copepod species to radiation was found to depend on the UV-B dose, resulting in higher mortality at the highest UV-B dose. Overall, at least one Boeckella species showed an acute sensitivity to increasing temperature, and the three species studied proved tolerant to the UV-B experimental exposure. The survivorship patterns observed in Boeckella species reflect clearly their adaptation to high solar radiation exposure and to temperate to cold environmental conditions. RESUMEN El objetivo de esta investigación es estudiar el impacto de las fluctuaciones de la temperatura y de la radiación ultravioleta (RUV) en tres especies de copépodos sudamericanos, Boeckella antiqua, B. gracilis y B. brevicaudata. La distribución geográfica de estas especies, restringida a latitudes altas de Sudamérica y a lagos de montaña en los Andes, indica su preferencia por ambientes templado-fríos. El aumento de temperatura y de los niveles de RUV a consecuencia del cambio climático impactarían partículannente a las especies estenotermas frías de lagos patagónicos. En este trabajo se reahzaron incubaciones de laboratorio de 10 y 2 días para analizar la mortalidad de Boeckella spp. en relación con: (i) la temperatura y, (ii) combinaciones de niveles de temperatura (5, 8, 12, 16, 20°C) y dosis )

Distribution of the genus Boeckella (Crustacea, Copepoda, Calanoida, Centropagidae) at high latitudes in South America and the main Antarctic biogeographic regions

“…Six of the 14 species of Boeckella occurring at high latitudes recorded in this study have been reported as exclusively distributed south of 40°S in South America ( B.brevicaudata , B.vallentini , B.silvestrii , B.antiqua Menu-Marque & Balseiro 2000, B.michaelseni and B.longicauda Daday 1901). In particular, B.silvestrii , reported from 44° to 50°S on the Argentine Patagonian Plateau (Menu-Marque et al 2000), and B.antiqua , which has never been recorded in any location since its original description from an ephemeral pond in Argentine grassland (Menu-Marque and Balseiro 2000; Pérez et al 2012; Garcia and Dieguez 2014). In contrast, other species showed much wider distributions, in particular B.poppei which has been reported across the three Antarctic biogeographical zones (sub-Antarctic islands, maritime and continental Antarctic), as well as in southern South America.…”

Oomycete parasites in freshwater copepods of Patagonia: effects on survival and recruitment

“…Annual rainfall in the area is 800 to 1400 mm, which largely determines the water regime of the pond. The hydroperiod of the pond generally lasts 8 to 9 mo (May to December), with maximum water levels registered in late autumn and winter and a maximum depth of 2 m. Water temperature ranges from 4°C in July and August (winter) to 20°C in December (Vega 1999, Garcia 2010.…”

“…The zooplankton assemblage is dominated by 3 endemic centropagid calanoid copepods: 2 genera of Boeckella (B. brevicaudata and B. gracilis) and Parabroteas sarsi, which develops exclusively from dormant eggs to adulthood (Dieguez & Balseiro 1998, Vega 1999. B. brevicaudata is present during the first half of the hydroperiod, coexisting briefly with adults of P. sarsi, whereas B. gracilis appears during the second half of the hydroperiod, coexisting with adults of P. sarsi throughout its life cycle (Garcia 2010). The cyclopoid copepods Acanthocyclops robustus and Tropocyclops prasinus meridionalis are also present in the pond but in low densities.…”

“…The cladocerans are represented by 3 species: Simocephalus serrulatus, Ceriodaphnia dubia and Daphnia commutata. Several species of rotifers and chydorids have also been registered there (Garcia 2010).…”

Record of parasitic oomycetes on neotropical copepods in aquatic environments of Northwestern Patagonia (Argentina)

“…On the other hand, temperature also affects physiology parameters such as metabolism level and oxygen consumption that, in turn, affect copepod's ability to resist environmental changes (Huntley & Lopez, 1992). High temperatures can accelerate metabolism and oxygen consumption, leading to excessive use of protein and a low survival rate (Li et al, 2009;Garcia & Diéguez, 2014). It is possible that a combination of these factors imposes severe restraints on P. sarsi females from spring onwards, differentially affecting their survival (Garcia et al, 2018).…”