Morphofunctional estimates to determine fish diversity in a highly heterogenic tidal flat (Araçá Bay, Brazil)
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1
Oceanographic Institute, University of São Paulo, Brazil
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2
Institute of Marine Sciences, Superior Council of Scientific Investigations, Spain
Species occurrence, functional roles, abundances and distributions are determined by resources available in the environment (as food, shelter, predation) and influence the ecosystem properties since they act in concert with abiotic factors (as temperature, depth, bottom type, disturbances). In turn, habitat structural heterogeneity provides a wide variety of microhabitats and niche spaces, which may support higher richness and morphological diversity. Fish assemblages in intertidal (IH), inner/outer sublittoral (IOS) and marginal shallow sublittoral (MSS) habitats of within a subtropical tidal flat were sampled with appropriate fishing gears. The objective of our study was to test if these habitats contain similar fish diversity and morphofunctional structures, and to verify what habitat(s) would be more sensitive in case of environmental degradation (the area has been threatened by a port expansion). To understand the species coexistence mechanisms and their functional responses, we applied geometric morphometric analysis (GMA) on eight categorical traits that describe the species functional strategies (body shape, swimming abilities, size, mobility, burying ability, diet, environment, and vertical distribution). Morphological and functional indexes were estimated. Our results reveal that habitat characteristics influence fish distribution and abundance in the tidal flat ecosystem being fish with distinct ecological strategies connected to specific components of the area. As expected, the species distribution within the morphospaces occurred according to their morphological features, explaining 96.8% of the total morphological variability. The morphospaces were built using the first two RWs, which explained around 70% of the total morphological variability. RW1 axis (41.71%) corresponded to the position and type of fins, and the head size. RW2 axis (28.58%) defined the relation between height and length of the body, characterizing the general shape profile. At IH habitat, elongated and fusiform shapes prevailed, adapted to live in water surface, with short dorsal fins beginning at the half of the body, and having prolonged heads. Most of these species were small to small-medium sized. At IOS habitat, the fish bodies were adapted to live on the bottom, presenting flattened shapes with elongated dorsal and anal fins, oval, oblong and deep-bodies laterally compressed; having small-medium to large sizes. At MSS, basically occurred fusiform shapes with adaptations to explore rock shores. Morphological indices (MD, MR and EMI) revealed a decreasing in ecomorphological diversity from IH to IOS and MSS, being the high value of first ones explained by the high abundance of Sardinella brasiliensis. The partitioning of the species into functional groups allowed to reveal 15 groups in IH, 11 groups in IOS, 8 groups in MSS. Vertical distribution, mobility and diet were the most relevant characters which in association with the body features, partitioned the species. The great deal of functional groups was attributed to the high morphological divergence among species and their feeding habits, as expected in highly heterogeneous ecosystems such as the Araçá bay. Functional spaces built by the first and second PCoA (Principal Coordinate Analysis) values represented 35.9% of the total functional variability. The PCoA1 axis (21.1 %) was associated to body shape, vertical distribution in the water column and species mobility. The PCoA2 axis (14.8 %), was related to swimming type and diet. In addition, the values of the functional indices (Functional evenness - Feve, Functional diversity – Fdiv, Functional richness – FR, and RaoQ) described how these functional groups use the habitats. In general, IH was strongly dominated by pelagic species, presented less shape redundancy (Ecomorphological Index - EMI= 0.45), mainly featured by elongated shapes, short dorsal fins beginning at the half of the body and big heads. The IOS were dominated by benthopelagic and benthic ones, presenting more redundancy (EMI= 0.03), with oval, oblong, flattened and deep-laterally compressed bodies. The MSS showed similar species with IOS (EMI= 0.05), however was important to represent the rocky shore species, with fusiform bodies. Regarding to functional diversity results, Feve evidenced broad occupation of the functional space by biological entities in IOS (0.61), indicating the well use of the resources. By contrast, the MSS functional space was underused suggesting low competition (Fdiv = 0.92) among the biological entities. The RaoQ designated the IH as the habitat with more distinct species abundance (RaoQ = 0.68) while MSS showed similar abundances but were distant inside the functional space (Fdis= 2.14, RaoQ= 4.75). According to the functional redundancy, among the three habitats, IOS (FR= 1.60) was more stable and resilient in case of a loss of the ecosystem functioning. The conclusion is that the three habitats deserve the species with functionally distinct manner, as nursery, food supply or protection. The proximity of IH to a remaining mangrove vegetation, the presence of two islets, its low hydrodynamics, and the constant change in its granulometry support a higher number of functional groups with little functional redundancy. Since functional redundancy acts as biological insurance against diversity loss, we can suppose that IH is most vulnerable to disturbances, even so with high-species diversity. The similarity between IH and IOS related to some functional groups and species composition, reinforce the idea of ecological connection between them. Considering IH habitat is essential in the tidal flat as an important feeding source for all fish assemblages, in case of it damage, the whole ecosystem functioning would be very affected.
Acknowledgements
São Paulo Research Foundation – FAPESP and CAPES Foundation (2014/20323-1 and 2014/26417-8).
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Keywords:
fish assemblage,
morphology,
functional traits,
habitat complexity,
Ecosystem functioning
Conference:
XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.
Presentation Type:
Poster
Topic:
ECOLOGY AND LIFE CYCLES
Citation:
Siliprandi
CC,
Tuset
V,
Farré
M,
Lombarte
A and
Wongtschowski
CR
(2019). Morphofunctional estimates to determine fish diversity in a highly heterogenic tidal flat (Araçá Bay, Brazil).
Front. Mar. Sci.
Conference Abstract:
XVI European Congress of Ichthyology.
doi: 10.3389/conf.fmars.2019.07.00022
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Received:
30 May 2019;
Published Online:
14 Aug 2019.
*
Correspondence:
Dr. Carolina C Siliprandi, Oceanographic Institute, University of São Paulo, São Paulo, São Paulo, 05508, Brazil, siliprandi@alumni.usp.br