Disentangling the hierarchical structure of environmental effects on fish assemblages in tropical coastal ecosystems
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1
Laboratory of Fish Ecology, Federal Rural University of Rio de Janeiro, Brazil
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2
Interdisciplinary Center for Marine and Environmental Research, Abel Salazar Institute of Biomedical Sciences, University of Porto, Portugal
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3
Fernando Pessoa University, Portugal
Understanding the processes driving the structure of coastal fish assemblages across space and time is of major relevance in the face of the increasing cumulative human impacts on food webs and ecosystem functioning. Factors in large scales, such as historical contingencies and contemporary climate changes, determine the species pool, which is gradually restricted by factors in smaller scales. Local assemblages are ultimately a result of the selection of species by local environmental conditions. The environmental effects at the site and landscape scales and spatial effects at three hierarchical levels (type of system, individual systems, and zones within each system) on the composition and abundance of species in two types of coastal ecosystems (coastal lagoons and bays) in Southeastern Brazil were investigated. Samples were obtained during the 2017 wet season (September, November, and January) in three coastal lagoons and three bays. In each ecosystem, sampling was performed at three zones with different distances from the ocean (inner, middle, and outer). Site-scale environmental measurements of water quality and substrate type were recorded concurrently with the fish sampling. Landscape-scale environmental metrics representative of land use and the number of close estuaries were obtained for each zone using a geographical information system. Species were classified in groups according to the habitat use (estuarine resident, marine migrant, marine straggle, semi-diadromous, and freshwater) and trophic guild (planktivores, benthophages, herbivores, detritivores, piscivores, and opportunists) to investigate if environmental effects differ depending on the degree of dependence from estuarine areas. The pure environmental effects of each variable set (site and landscape scales) and the fractions shared with the hierarchical levels were accessed by variance partitioning. The relevance of individual environmental variables was quantified by partial canonical correspondence analysis (pCCA) controlling for the hierarchical structure. Prior to the analyses, a forward selection procedure based on the adjusted R² and a nominal p-value of 0.05 to indentify a parsimonious subset of environmental predictors to be included in the pCCA models using the hierarchical levels as conditioning terms were used. For all cases, as the investigation was focused on spatial patterns, the effect of the period of sampling was controlled. The variance inflation value < 4 for all variables indicated that no model was biased by collinearity between the environmental predictors. According to the variance partitioning, landscape-scale variables explained more of the variance in the composition and abundance of species (26%) than site-scale variables (16%). However, an expressive fraction was shared between both variable sets (6%) and with the hierarchical spatial structure (7%), with the later influencing a total of 19% of the species variance. Marine migrant species were primarily associated with higher number of close estuaries, distance from the ocean and mangrove cover, indicating a positive relationship with the continental influence and the availability of estuarine habitats. Marine straggle species were primarily associated with higher values of salinity, depth and transparency, evidencing the relevance of a higher marine influence for that group. Freshwater species and on a lesser extent estuarine resident and semi-diadromous species were associated with the opposite gradients, with the later groups distributed across the environmental gradients, but primarily associated with intermediate conditions. In general, these relationships did not change controlling for the influence of the hierarchical structure, but a greater relevance of the mangrove cover was observed for the semi-diadromous and estuarine resident species. Regarding to the trophic guilds, the species were, in general, distributed across all the environmental gradients. A group of benthophages, planktivores and piscivores was primarily associated with higher salinity, transparency and depth, whereas other group was more associated with a higher number of close estuaries, distance from the ocean, and mangrove cover. The opportunists were primarily associated with lower transparency, depth, and salinity, but also with higher mangrove cover. Controlling for the effect of the hierarchical spatial structure, piscivores were primarily associated with a higher marine influence, whereas a especially benthophages, detritivores and opportunists, but also planktivores were primarily associated with intermediate to higher values of the mangrove cover. Herbivores were also positively associated with the mangrove cover, but primarily with intermediate to higher number of close estuaries. These results evidenced the relevance of disentangling spatial and environmental effects for a better understanding of the major determinants of the structure of fish assemblages in different types of coastal ecosystems. The availability of estuarine habitats was of major relevance for the composition and abundance of species with different degrees of dependence from estuarine areas. Therefore, actions focusing on the conservation of the mangrove cover and the maintenance of the connectivity with close estuaries are critical for fish assemblages in different types of coastal ecosystems.
Acknowledgements
This study was supported by FUNBIO – Fundo Brasileiro para a Biodiversidade, Programme for Marine & Coastal Research (Edital 05/2016). Other Institutions gave support for the development of this Project, namely Ministério do Meio Ambiente through the IBAMA – Instituto Brasilieiro de Meio Ambiente and Ministério Público Federal, Brazil and ANP – Agência Nacional de Petróleo, Gás Natural e Biocombustíveis. The Strategic Funding UID/Multi/04423/2019 provided by FCT and ERDF (PT2020) is acknowledge.
Keywords:
Hierarchical spatial structure,
scale dependence,
multi-scale environmental effects,
land use,
fish,
Coastal zone
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Poster Presentation
Topic:
Ecology, Biodiversity and Vulnerable Ecosystems
Citation:
Camara
EM,
Andrade-Tubino
MF,
Franco
TP,
Correia
AT and
Araújo
FG
(2019). Disentangling the hierarchical structure of environmental effects on fish assemblages in tropical coastal ecosystems.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00136
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Received:
18 May 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Mx. Francisco G Araújo, Laboratory of Fish Ecology, Federal Rural University of Rio de Janeiro, Seropédica, Brazil, gersonufrrj@gmail.com