Mudflat surface morphology as a structuring agent of algae and associated macroepifauna communities: A case study in the Ria Formosa

Abstract

Although mudflats seem relatively planar, closer inspection reveals a succession of meso-topographical features, including consecutive convex and concave meso-and micro-topographical features. The objective of this study was to determine the influence of meso-scale surface sediment morphology on the dynamics of the macroalgae Ulvales (Chlorophyta) and associated macroepifauna in the Ria Formosa tidal lagoon (Southern coast of Portugal). Sampling took place at four sites in the Ria Formosa with monthly periodicity. Two were located on convex sections (mounds) of the mudflat and the other two on concave sections (depressions)., Macroalgae and related macroepifauna were sampled at each station. Biomass was quantified by determination of the ash-free dry weight (AFDW). Data were analysed using the software package "PRIMER" (Plymouth Routines In Multivariate Ecological Research). Results show a clear distinction between convex and concave areas. In † deceased 2 convex sections, Enteromorpha dominated, to the point of being the only algal species present during part of the year. Conversely, biomass and dynamics of Enteromorpha and Ulva were almost the same in concave sections. The associated macroepifauna was also different in protruding or depression sections of the mudflat. In the convex areas, the macroepifauna population showed less diversity and was dominated by the snail Hydrobia ulvae. In concave areas, the species diversity was larger, but dominated in terms of biomass by the amphipod Melita palmata and the gastropod Nassarius pfeifferi. Results of the study indicate that the benthic communities associated with concave or convex features were different. No relevant differences in texture and sediment physico-chemical characteristics were found between convex and concave sections of the sampling sites. The inference is that the morphological nature of the bottom in tidal mudflats can act as a structuring agent of benthic communities.

Monitoring invasive macroalgae in southern Portugal: drivers and citizen science contribution

“…While the western and central south coast of Algarve is characterized by rocky shores with pockets of sandy beaches and cliffs, the eastern zone is mostly sandy (Moura et al, 2006), including the Ria Formosa Barrier Island System with its coastal lagoon. The Ria Formosa lagoon encompasses a large region of intertidal mudflats where Ulva genus is predominant (Aníbal et al, 2007). The hydrodynamic patterns of the lagoon at Ria Formosa are primarily influenced by tides and wind (Mudge et al, 2008;Jacob and Cravo, 2019).…”

Interaction strength between different grazers and macroalgae mediated by ocean acidification over warming gradients

“…They can be found associated to mixed macroalgal beds, including large accumulations of Ulva spp., searching for food and refuge during low intertidal. The green seaweeds from the Ulva genus are very common opportunistic primary producer in shallow coastal waters and tidal pools in rocky shore communities (Aníbal et al, 2007).…”

A halocarbon survey from a seagrass dominated subtropical lagoon, Ria Formosa (Portugal): flux pattern and isotopic composition

“…Moreover, this potential variation of source contribution can be further assumed by the certain change between summer and spring where e.g. macroalgae are more abundant in the latter period (Anibal et al, 2007). Already reported source signatures of phytoplankton, macroalgae, and seagrass meadows cover the range of −10 to −23 ‰ (Auer et al, 2006;Weinberg et al, 2013), thus demonstrating differences in their isotopic fingerprint.…”