Reef flattening effects on total richness and species responses in the Caribbean

Abstract

There has been ongoing flattening of Caribbean coral reefs with the loss of habitat having severe implications for these systems. Complexity and its structural components are important to fish species richness and community composition, but little is known about its role for other taxa or species-specific responses. This study reveals the importance of reef habitat complexity and structural components to different taxa of macrofauna, total species richness, and individual coral and fish species in the Caribbean. Species presence and richness of different taxa were visually quantified in one hundred 25-m(2) plots in three marine reserves in the Caribbean. Sampling was evenly distributed across five levels of visually estimated reef complexity, with five structural components also recorded: the number of corals, number of large corals, slope angle, maximum sponge and maximum octocoral height. Taking advantage of natural heterogeneity in structural complexity within a particular coral reef habitat (Orbicella reefs) and discrete environmental envelope, thus minimizing other sources of variability, the relative importance of reef complexity and structural components was quantified for different taxa and individual fish and coral species on Caribbean coral reefs using boosted regression trees (BRTs). Boosted regression tree models performed very well when explaining variability in total (82·3%), coral (80·6%) and fish species richness (77·3%), for which the greatest declines in richness occurred below intermediate reef complexity levels. Complexity accounted for very little of the variability in octocorals, sponges, arthropods, annelids or anemones. BRTs revealed species-specific variability and importance for reef complexity and structural components. Coral and fish species occupancy generally declined at low complexity levels, with the exception of two coral species (Pseudodiploria strigosa and Porites divaricata) and four fish species (Halichoeres bivittatus, H. maculipinna, Malacoctenus triangulatus and Stegastes partitus) more common at lower reef complexity levels. A significant interaction between country and reef complexity revealed a non-additive decline in species richness in areas of low complexity and the reserve in Puerto Rico. Flattening of Caribbean coral reefs will result in substantial species losses, with few winners. Individual structural components have considerable value to different species, and their loss may have profound impacts on population responses of coral and fish due to identity effects of key species, which underpin population richness and resilience and may affect essential ecosystem processes and services.

Long-term Shifts in Coral Communities On Shallow to Deep Reef Slopes of Curaçao and Bonaire: Are There Any Winners?

“…An important consequence of reduced coral cover is the loss of reef structural complexity and associated loss of biodiversity, but also coastal protection and human food security (e.g., AlvarezFilip et al, 2009;Newman et al, 2015). In many of the studied quadrats, coral cover has approached or dropped below the 10% level.…”

“…The calcification balance on many of these reefs may currently have shifted toward net erosion which will result in the reduction of architectural complexity (Alvarez-Filip et al, 2009;Kennedy et al, 2013;Perry et al, 2013). This may drastically alter reef functioning and lead to loss of biodiversity as well as a reduction in important ecosystem services for coastal human population such as wave protection and food security (Moberg and Rönnbäck, 2003;Alvarez-Filip et al, 2009, 2011bGraham and Nash, 2013;Newman et al, 2015).…”

Extinction risk and conservation of marine bony shorefishes of the Greater Caribbean and Gulf of Mexico

“…For example, of the 11 coralbrotulas (Bythitidae), small, cryptic fishes that inhabit interstitial spaces in coral reef, one is threatened because of susceptibility to reef complexity loss and four are DD through a lack of information. Many Greater Caribbean reef specialists, especially small‐bodied species, use coral reefs for shelter and food, and are likely to undergo population declines because of the region‐wide loss of coral cover and changes in coral assemblages (Alvarez‐Filip, Paddack, Collen, Robertson, & Côté, ; Newman et al, ; Rogers, Blanchard, & Mumby, ). Nearshore marine habitats such as hard bottom, which can support coral reef development, also support juveniles of many reef species that ontogenetically distribute across the shelf with development, and are designated as Essential Fish Habitat and Habitat Areas of Particular Concern according to the US South Atlantic Fishery Management Councils.…”

Staat van de natuur van Caribisch Nederland 2017 : een eerste beoordeling van de staat (van instandhouding), bedreigingen en managementimplicaties van habitats en soorten in Caribisch Nederland

“…Dit maakt ze erg kwetsbaar voor beïnvloeding vanaf het land. In geheel Caribisch Nederland, inclusief de Saba Bank, zijn de riffen in afgelopen decennia ernstig achteruitgegaan (Bak et al, 2005;Newman et al, 2015;. Dit komt door een combinatie van factoren waaronder zowel natuurlijke als menselijke factoren .…”