Spatial and temporal variability of the zooplankton community in Valdés Biosphere Reserve, Patagonia, Argentina: Nuevo Gulf case study

https://doi.org/10.1016/j.csr.2021.104478Get rights and content

Highlights

  • Mesozooplankton community is represented mostly by calanoid copepods, contrasting with previous studies in the Nuevo Gulf (NG).

  • Community composition varies from spring to summer within the NG.

  • Large copepods (but not their sex ratio) were the only group showing differences between depth layers and seasons.

  • Drepanopus forcipatus was registered for the first time in the study area.

Abstract

Zooplankton diversity has been identified as one of the biological Essential Ocean Variables to detect temporal and spatial changes in marine biodiversity and ecosystem health. The present study evaluated the mesozooplankton community composition and abundance associated with oceanographic variables in Nuevo Gulf (NG, 42° 42′S, 64° 30′W), a World Heritage Site in Argentinian Patagonia and part of the Valdés Biosphere Reserve. We found that >43% of total mesozooplankton community abundance was composed by copepods, followed by cladocerans (24%) in spring, while copepods represented more than 98% in summer. Variability of the abundances in most mesozooplankton groups was associated with chlorophyll a and temperature values. Among copepods, Calanoida predominated in the community, mainly reflecting high densities of Ctenocalanus vanus, especially in summer. In addition, we report for the first time the presence of the copepod Drepanopus forcipatus in this Gulf. Zooplankton information for this region is scarce and fragmented, thus a short review of previous mesozooplankton studies from nearby areas is included for context. Our work emphasizes the importance of continuous and long-term monitoring to better understand the zooplankton community under expected environmental changes.

Introduction

Zooplankton is a key component in marine ecosystems, transferring energy from primary producers to higher trophic levels and contributing to the overall biogeochemical cycles (Calbet and Saiz, 2016). Zooplankton diversity and biomass were both identified as biological Essential Ocean Variables (EOVs) due to their ecological relevance and their potential to inform about environmental changes that may have societal importance (Miloslavich et al., 2018). Therefore, monitoring plankton in general is important because these organisms constitute the base of the marine food web, play important roles in biogeochemical cycles, thus in the global climate, being at the same time sensitive to ecosystem perturbations (Muller-Karger et al., 2013, 2018).

The Argentine Patagonian shelf presents high biological productivity and biodiversity (Bisbal, 1995; Gregg et al., 2005; Sherman and Duda, 1999), supporting a large fishing activity and being an important breeding area for marine mammals and seabirds (Acha et al., 2019; Gregg et al., 2005; Sánchez and Bezzi, 2004). The Valdés Biosphere Reserve (VBR) encompasses the Patagonian steppe and Argentine Sea eco-regions, where fragile ecosystems are present. There is therefore a need to protect their key species, especially considering that the coastal marine environment is affected by increasing anthropogenic stress. In the last decades, important changes have been registered in the Southwest Atlantic Ocean, including surface and subsurface ocean warming (Franco et al., 2020). Warming can affect pelagic ecosystems in complex ways, including shifting patterns of species, changing biogeographical ranges and decreasing energy transfer efficiency (Gamfeldt et al., 2015).

Recent works have compiled and described mesozooplankton distribution known to date in some regions of the Argentinian Shelf (e.g. Acha et al., 2019; Cepeda et al., 2018; Dutto et al., 2019), highlighting that data is still scarce and poor “insufficiently studied” for some of the taxonomic groups (Boltovskoy and Valentin, 2018). In particular, these works did not include the study of the north Patagonian gulfs forming the VBR, i.e., the San José Gulf (SJG) and the Nuevo Gulf (NG), which are areas of great importance for marine conservation. These gulfs are located in the Valdés Peninsula Protected Area, a natural reserve designated as a World Heritage Site and Biosphere Reserve by the United Nations Educational, Scientific and Cultural Organization (UNESCO 1999). The VBR is recognized worldwide as an essential habitat for marine mammals and other top predators, which have been studied for several decades now (Crespo et al., 2019; Degrati et al., 2020; Jarma et al., 2019). In contrast, despite the ecological importance of zooplankton for this ecosystem, its composition and variability are not yet well characterized. In addition, recently D'Agostino et al. (2019) showed that mesozooplankton, mainly calanoid copepods, are the primary potential vector of phycotoxins in the pelagic food web, accumulating and transferring toxins within the system, which highlights the importance of systematic monitoring of the zooplankton composition and abundance. There is in addition a need for baseline information to allow the detection of changes in the pelagic food web and elucidate possible effects on the marine ecosystem as a whole. The aim of this study is to contribute to this baseline and provide further knowledge on the mesozooplankton community composition and distribution within the NG in relation to environmental variables during austral spring and summer. We further include a short review of all zooplankton studies conducted in NG to date.

Section snippets

Study site

The NG (42° 42′ S, 64° 30’ W) is a semi-enclosed basin with a surface area of 2400 km2, an average depth of 80 m and maximum depth of 180 m (Rivas and Beier, 1990). It has a narrow (16 km) opening and a shallow sill which restrict the exchange of water with the open sea, so the waters in the NG are consequently more influenced by atmospheric forcing than by shelf waters (Rivas, 1990; Rivas and Ripa, 1989, Fig. 1). The extended residence time in the Gulf results in a greater annual thermal

Hydrography

Mean temperature was higher in summer (p < 0.05), both in the surface layer (16.55 °C ± 0.58) and intermediate layer (12.75 °C ± 0.33), compared to the spring season (11.20 °C ± 0.4 and 10.67 °C ± 0.25 for surface and intermediate layers, respectively; Table 1). Salinity was homogeneous, with no variations with station, seasons or depth (p = 0.89), with an average value of 33.98 psμ ± 0.04 (values for all stations are shown in Table 1).

The average Chl a concentration was higher (p < 0.05) in

Discussion

The importance of the Valdés Biosphere Reserve. Marine protected areas have been recognized for their value enhancing the conservation, including the preservation of genetic resources, key species, critical ecosystem and landscapes, while providing the scientific knowledge and human values to support sustainable development and management (Claudino-Sales, 2019; Ishwaran et al., 2008; Reed, 2016). Only a few studies conducted in the Valdés Biosphere Reserve (VBR; Deguignet et al., 2014) analyzed

Conclusions

Baseline environmental and biological data are essential to understand how species and habitats would respond to natural and man-made variations. Although plankton studies in the NG date back to the 90s, and variations of large mesozooplankton groups may be noted, the lack of sustained monitoring makes temporal interpretations difficult. Mesozooplankton distribution in the NG varies during the year and this variation is essentially determined by seasonal characteristics, especially high

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We would like to thank G. Bravo, G. Trobbiani, L. Epherra, N. Ortíz, R. (Bebo) Vera, J. Crespi and JP. Pisoni for the fieldwork planning and collection of the samples, as well as C. Derisio and A. Berasategui for their time and help with zooplankton identification. We thank A. Baldoni and INIDEP for salinity samples analysis. We are grateful to the LAMAMA and LOQyCA groups (CESIMAR) for providing laboratory facilities. We also thank P. Bermejo and G. Williams for helping us to measure Chl a.

References (66)

  • B. Temperoni et al.

    Spatial patterns of copepod biodiversity in relation to a tidal front system in the main spawning and nursery area of the Argentine hake Merluccius hubbsi

    J. Mar. Syst.

    (2014)
  • E.M. Acha et al.

    Large-scale geographic patterns of pelagic copepods in the southwestern South Atlantic

    J. Mar. Syst.

    (2019)
  • J.C. Antacli et al.

    Feeding and reproductive activity of the copepods Drepanopus forcipatus and Calanus australis during late summer on the Southern Patagonian shelf (Argentina, 47°-55°s)

    Braz. J. Oceanogr.

    (2014)
  • M.F. Baumgartner et al.

    The physiology and ecology of diapause in marine copepods

    Ann. Rev. Mar. Sci.

    (2017)
  • A.A. Berasategui et al.

    Mesozooplankton structure and seasonal dynamics in three coastal systems of Argentina: Bahía Blanca estuary, Pirámide Bay, and Ushuaia Bay

    (2018)
  • D. Boltovskoy

    South Atlantic Zooplankton

    (1999)
  • D. Boltovskoy

    Atlas del zooplancton del Atlántico Sudoccidental y métodos de trabajo con el zooplancton marino

    (1981)
  • D. Boltovskoy et al.

    Overview of the History of Biological Oceanography in the Southwestern Atlantic, with Emphasis on Plankton

  • A. Calbet et al.

    Introduction: role of zooplankton in marine biogeochemical cycles: from fine scale to global theories

    J. Plankton Res.

    (2016)
  • G.D. Cepeda et al.

    Zooplankton communities of the Argentine continental shelf (SW Atlantic, ca. 34°-55°S), an overview

    Plankt. Ecol. Southwest. Atl. From Subtrop. to Subantarctic Realm

    (2018)
  • P.M. Cervellini

    Las larvas y postlarvas de los crustáceos Decapoda en el estuario de Bahía Blanca. Variaciones estacionales y su relación con los factores ambientales (Ph.D. Thesis)

    (1988)
  • V. Claudino-Sales

    Coastal World Heritage Sites

    (2019)
  • E.A. Crespo et al.

    The southwestern Atlantic southern right whale, Eubalaena australis, population is growing but at a decelerated rate

    Mar. Mamm. Sci.

    (2019)
  • V.C. D'Agostino et al.

    Faecal analysis of southern right whales (Eubalaena australis) in Península Valdés calving ground, Argentina: Calanus australis, a key prey species

    J. Mar. Biol. Assoc. U. K.

    (2016)
  • V.C. D'Agostino et al.

    Occurrence of toxigenic microalgal species and phycotoxin accumulation in mesozooplankton in Northern Patagonian Gulfs, Argentina

    Environ. Toxicol. Chem.

    (2019)
  • K.L. Daly et al.

    Physical-biological interactions influencing marine plankton production

    Annu. Rev. Ecol. Systemat.

    (1993)
  • K.L. Daly et al.

    Physical-biological interactions influencing marine plankton production

    Annu. Rev. Ecol. Systemat.

    (1993)
  • M. Degrati et al.

    Integrating multiple techniques to estimate population size of an impacted Dusky Dolphin's population in Patagonia, Argentina

    Front. Mar. Sci.

    (2020)
  • M. Deguignet et al.

    Liste des Nations Unies des Aires Protégées 2014

    (2014)
  • F.G. Dellatorre et al.

    Seasonal abundance and vertical distribution of crab larvae from northern Patagonia (Argentina): implications for their transport in a biogeographic boundary region

    Mar. Biol. Res.

    (2014)
  • R. Di Mauro et al.

    Capture efficiency for small dominant mesozooplankters (Copepoda, Appendicularia) off Buenos Aires province (34°S-41°S), Argentine Sea, using two plankton mesh sizes

    Braz. J. Oceanogr.

    (2009)
  • M.S. Dutto et al.

    Macroscale abundance patterns of hydromedusae in the temperate Southwestern Atlantic (27–56 S)

    PLoS One

    (2019)
  • N.C. Fernandez Araoz

    Individual biomass, based on body measures, of copepod species considered as main forage items for fishes of the Argentine Shelf

    Oceanol. Acta

    (1991)
  • Cited by (2)

    View full text