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Zooplankton Community Attributes in an Oligo-Mesotrophic Reservoir: a Comparative Study of Two Sampling Strategies

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Zooplankton Community Attributes in an Oligo-Mesotrophic Reservoir: a Comparative Study of Two Sampling Strategies Anais da Academia Brasileira de Ciências (2019) 91(1): e20170807 (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690 http://dx.doi.org/10.1590/0001-3765201820170807 www.scielo.br/aabc | www.fb.com/aabcjournal Zooplankton community attributes in an oligo-mesotrophic reservoir: A comparative study of two sampling strategies RAFAEL L. MACÊDO1, VANESSA G. LOPES2, BETINA KOZLOWSKY-SUZUKI3 and CHRISTINA W.C. BRANCO1 1Núcleo de Estudos Limnológicos, Departamento de Zoologia, Instituto de Biociências, Centro de Ciências Biológicas e da Saúde, Universidade Federal do Estado do Rio de Janeiro/UNIRIO, Av. Pasteur, 458, 22290-240 Rio de Janeiro, RJ, Brazil 2Laboratório de Ecologia Teórica e Síntese/LETS, Instituto de Ciências Biológicas/ICB, Universidade Federal de Goiás/UFG, Av. Esperança, s/n, 64690-900 Goiânia, GO, Brazil 3Departamento de Ecologia e Recursos Marinhos, Instituto de Biociências, Centro de Ciências Biológicas e da Saúde, Universidade Federal do Estado do Rio de Janeiro/UNIRIO, Av. Pasteur, 458, 22290-240 Rio de Janeiro, RJ, Brazil Manuscript received on October 13, 2017; accepted for publication on May 31, 2018 How to cite: MACÊDO RL, LOPES VG, KOZLOWSKY-SUZUKI B AND BRANCO CWC. 2019. Zooplankton community attributes in an oligo-mesotrophic reservoir: A comparative study of two sampling strategies. An Acad Bras Cienc 91: e20170807. DOI 10.1590/0001-3765201820170807. Abstract: Studies of the limnetic zooplankton in Brazilian freshwater have been done using several sampling strategies which are frequently associated to personal preferences, system constraints and objectives of the studies. It is known that a better sampling technique exists for each group of investigated zooplankton. So, the challenge is to provide a good sampling method for all groups at once. Regarding this theme we are contributing by pointing out the merits and demerits of two collecting methods of zooplankton widely used in many studies in Brazilian reservoirs to clarify the information about communities’ structure in past published and non-published biological data and also find a more useful sampler for future studies. Two simultaneous strategies were used with a 68μm-plankton net: filtration of water collected at sub- surface by bucket and vertical hauls throughout the euphotic zone. A total of 133 taxa was found with both strategies. Rotifers (69 taxa) comprised the group with the highest richness, followed by protozoans (31 taxa), cladocerans (30 taxa) and copepods (5 taxa). Paired t-tests showed significant difference for richness despite none for density in whole period. Spatially, sampling strategies differed in abundance and composition of zooplankton at most sites sampled (except for L1- shallowest site and L4 – deepest site). Temporally, both samplers showed the highest mean abundances at thermal stratification period. In general, the extent of spatial data collected throughout the vertical gradient provided better estimations in the limnetic area for the attributes analyzed: zooplankton density, richness, specific diversity, equitability and cumulative richness. Zooplankton sampling by vertical hauls through the euphotic zone was more efficient, but in order to obtain integrated data and according to the collector’s curve it might be useful to adopt both methodologies. Key words: bucket sampling, freshwater mesozooplankton, plankton collection methods, sub-sampling, vertical hauls. Correspondence to: Rafael Lacerda Macêdo E-mail: [email protected] ORCid: http://orcid.org/0000-0001-5086-0170 BIOLOGICAL SCIENCES An Acad Bras Cienc (2019) 91(1) RAFAEL L MACÊDO et al. COMPARISON OF ZOOPLANKTON SAMPLING TECHNIQUES INTRODUCTION and Fraundorf 1966, Vannucci 1968), and protozoa- surface collections (Lahr and Lopes 2006). While Zooplankton communities can vary over both species richness and evenness are usually dependent spatial and temporal gradients and this variation on mesh size, diversity indexes are typically less is often difficult to be quantified statistically influenced by mesh selection (Riccardi 2010, Wu (Evans and Sell 1983, Livings et al. 2010). This et al. 2011). The fact is that the effectiveness of variability may affect the accuracy and precision of filter material for the separation of plankton size the estimation of zooplankton populations and the fractions has been discussed since long (Evans and diagnosis of community shifts in response to local Sell 1985, Logan 1993, Hwang et al. 2007, Wu et gradients and temporal environmental changes. al. 2011). So, the challenge is to provide a good Sampling strategies that do not consider spatial sampling method for all groups at once. and temporal structuring of communities lead to Kozlowsky-Suzuki and Bozelli (1998) poorly designed surveys that may significantly compared the efficiency of three different underestimate diversity (Vieira et al. 2017). samplers (vertical haul, Schindler-Patalas trap and Studies of the limnetic zooplankton in suction pump) in a Brazilian coastal lagoon. The Brazilian natural lakes and reservoirs have been performance of the vertical haul with plankton net done using several sampling strategies such as was the lowest, except for the copepods, and the collecting a known volume of sub-surface water by sampling with suction pump was considered the bucket or by bottle-sampler and filtration through most efficient for all the taxa analyzed. However, a plankton net (Rocha et al. 2002, Almeida et al. several authors agree that adopting only a single 2006, 2009, Peixoto et al. 2008, Nadai and Henry collecting strategy might not satisfactorily sample 2009), collecting with a suction pump (Sampaio et all components of the zooplankton community al. 2002, Takahashi et al. 2005, Santos-Wisniewski (Hodgkiss 1977, Starling 2000, Livings et al. 2010). and Rocha 2007, Serafim-Jr et al. 2010), sampling Vertical haul has been the most used technique at several depths using a Van Dorn bottle followed in studies of zooplankton communities in reservoirs, by filtration (Starling 2000, Maia-Barbosa et al. and according to Tonolli (1971) it is the method 2003, Keppeler 2003), collection by vertical hauls that achieves the most accurate representation of with a plankton net at specific layers of the water the total plankton present in the water column, column (Maia-Barbosa and Bozelli 2005, Sendacz since it enables a larger volume of water to be et al. 2006, Nogueira et al. 2008, Simões and sampled at various depths. The collection by Sonoda 2009, Silva et al. 2014), horizontal hauls suction pump, despite filtering large volumes of at surface (Waichman et al. 2002) or sampling water in a short time, has limitations in terms of using a Schindler-Patalas trap (Pinto-Coelho et al. selectivity of zooplankton taxa and is not optimal in 2005, Bezerra-Neto et al. 2009). These varieties deep systems. The continuous constant flow selects of techniques are frequently also associated to a larger quantity of poor swimmers, the suction personal preferences, system constraints and the may damage illoricated rotifers or address the objectives of different zooplankton community problem of collecting live specimens for mortality studies (Mack et al. 2012). determination (Icanberry and Richardson 1973), It is known that a best sampling technique and the narrow diameter of the collector tube helps exists for each group of zooplankton investigated the scape of the good swimmers. Furthermore, as (for example: macrozooplankton - large mesh net, discussed by Di Bernardi (1984) suction by pump microzooplankton - small mesh nets (MacGowan precludes the knowledge on the heterogeneous or An Acad Bras Cienc (2019) 91(1) e20170807 2 | 17 RAFAEL L MACÊDO et al. COMPARISON OF ZOOPLANKTON SAMPLING TECHNIQUES in mosaic distribution of the zooplankton, as well immediate filtration. Here, we aim at characterizing as the vertical haul. in the zooplankton community at two different However, both the vertical hauls and the environments in the water column based on two collection of large volumes of water through the different sampling methods at an oligo-mesotrophic suction pump can be impractical in eutrophic reservoir considering attributes such as richness, reservoirs due to the ease clogging of the plankton abundance, frequency of occurrence, evenness and net by phytoplankton. In particular when the mesh diversity of taxa. <200μm is used, the high biomass of phytoplankton We predict that the method of collecting such as cyanobacteria colonies and/or filaments zooplankton at the subsurface, although more agile, often impair filtration of large volumes of water. practical and adopted in systematic monitoring In these environments, the most used strategy for in many eutrophic reservoirs might significantly zooplankton sampling has been the collection of subsample the zooplankton community in limnetic a small volume of water for further filtration, as area of this oligo-mesotrophic reservoir. This could in the studies of Rocha et al. (2002) and Branco be due to the smaller sampling area (subsurface), et al. (2002) in the Funil reservoir (20L), Branco not to mention the probable greater escape of and Senna (1996) in Lake Paranoá (20L) or by mobile taxa. the Schindler-Patalas trap (5.1L) as in the study of Pinto-Coelho et al. (2005) in the Pampulha MATERIALS AND METHODS reservoir. However, in addition to the low volume, STUDY AREA another question has been considered Schwoerbel (1970) when using collection by bottles, buckets Ribeirão das Lajes Reservoir
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