Endemic fish species structuring oceanic intertidal reef assemblages

Abstract

Intertidal reef environments are facing a global crisis as climate changes are causing sea-level rise. Synergistically, other human-induced impacts (e.g., sewage, habitat loss) caused by concentration of human populations near the coast increase the natural vulnerability of intertidal ecosystems. However, the effect of these threats have long been neglected due, in part, to a limited knowledge of some aspects of intertidal fish ecology. We tested what are the main differences and drivers in fish assemblages structure between tidepools in three oceanic and three continental shelf (coastal) sites of the tropical southwestern Atlantic (Brazilian Province) using standardized sampling methods. Oceanic and coastal fish assemblages were distinctly structured at the trophic and composition levels. The noteworthy endemism species rate (38–44%) and high densities in oceanic sites are supported by resident species restricted to mid and high-shore tidepools where herbivores were the major trophic group. The coastal sites, on the other hand, were dominated by widely distributed and carnivore species. Physical (substrate type, pool height, subtidal distance and rock coverage), biological (sessile animal coverage) and chemical (salinity) parameters act as the driving forces influencing fish spatial occupancy. Here, clear evidences of high fish endemism and importance of endemics structuring oceanic communities may act as the last straw in favor of the conservation of oceanic intertidal reefs.

Intertidal Biogeographic Subprovinces: Local and Regional Factors Shaping Fish Assemblages

“…Bathygobius soporator was distributed in all subprovinces, but at particularly high mean densities at the AE sites (225.9 individuals per m 3 ), which is likely related to its preference for tidepools with estuarine features (Macieira and Joyeux, 2011;Oliveira et al, 2016). By contrast, B. geminatus, which is distributed between Florida and the TW subprovince, typically inhabits classical marine tidepools (Macieira and Joyeux, 2011;Andrades et al, 2018), and is absent from the AE and NM sites, while increasing in density toward the south. The subprovincial endemism of tidepool fishes in the AE also highlights the local features that act as barriers.…”

“…7,490 km, from 4 • N to 34 • S (Figure 1), with an enormous diversity of climatic, geomorphologic, oceanographic, and ecologic features. As the ecological dynamics of classic rocky shores and flat intertidal reefs are distinct (Mahon and Mahon, 1994;Macieira and Joyeux, 2011;Andrades et al, 2018), the present study surveyed sites between 0 • S and 21 • S, which encompasses the transition of intertidal flat reefs to rocky shore (slope is present).…”

“…Intertidal fish communities may vary in response to latitude (see Harasti et al, 2016), however, local factors (e.g., substrate composition, water temperature, tidepool morphology, and height above sea level) may also have a strong influence on the distribution of fish species (Mahon and Mahon, 1994;Arakaki and Tokeshi, 2011;Macieira and Joyeux, 2011;White et al, 2015), even in a large-scale setting (Arakaki et al, 2014). Even so, the paucity of the data available for this vulnerable environment, which is at risk from both local and global impacts, is a major drawback (Helmuth et al, 2002(Helmuth et al, , 2006Thompson et al, 2002;Halpern et al, 2008;Vinagre et al, 2016;Andrades et al, 2017Andrades et al, , 2018. In general, the large-scale distribution of species can be explained by dispersal capacity and geographic patchiness , while community patterns at a local scale are driven strongly by local environmental characteristics, such as substrate type, the morphology of tidepools, and oceanographic features (Gibson and Yoshiyama, 1999;Cox et al, 2011).…”

“…These studies have identified a number of local factors that structure fish assemblages on the Brazilian coast, but only Pinheiro et al (2018) has discussed in detail the role of ecological and evolutionary processes in the fish distribution and proposed a set of biogeographic subprovinces based on the existing configuration of the Brazilian Province (sensu Briggs and Bowen, 2012). As intertidal habitats on the tropical Brazilian coastline are used by subtidal marine and estuarine fish species, also as nursery habitats or during their whole life-cycle (Macieira and Joyeux, 2011;Andrades et al, 2018), it is reasonable to expect that the intertidal fish fauna is highly influenced by local factors, resulting in more heterogeneous and complex biogeographic patterns than previously observed in reef fishes (Pinheiro et al, 2018).…”

Peer Review #2 of "Substrate rugosity and temperature matters: patterns of benthic diversity at tropical intertidal reefs in the SW Atlantic (v0.1)"

“…Our findings indicate that rugosity is not only a useful tool for biodiversity mapping in reef intertidal ecosystems but also that spatial differences in rugosity would lead to very distinct biogeographic and temporal patterns. This study offers a unique baseline of benthic biodiversity on coastal marine habitats that is complementary to worldwide efforts to Introduction Marine benthic ecosystems hold a significant portion of global biodiversity that is mostly concentrated in threatened coastal habitats such as intertidal reefs (Halpern et al, 2008;Andrades et al, 2018). There are high concerns of human impacts on marine biodiversity across a range of expected climate change scenarios (Dulvy et al, 2003;Solan et al, 2004;Harnik et al, 2012;McCauley et al, 2018).…”