Reef flattening effects on total richness and species responses in the Caribbean.
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.
School of Marine Science and Technology, Newcastle University, Newcastle, NE1 7RU, UK.
Steven P
SP
Newman
Institute for Marine Resources and Ecosystem Studies, IMARES, 1790AD, Den Burg, The Netherlands.
Erik H
EH
Meesters
School of Marine Science and Technology, Newcastle University, Newcastle, NE1 7RU, UK.
Charlie S
CS
Dryden
Centro de Investigación en Ciencias del Mar y Limnología and Escuela de Biología, Universidad de Costa Rica, San Pedro, 11501-2060, San José, Costa Rica.
Stacey M
SM
Williams
Centro de Investigación en Ciencias del Mar y Limnología and Escuela de Biología, Universidad de Costa Rica, San Pedro, 11501-2060, San José, Costa Rica.
Cristina
C
Sanchez
Marine Spatial Ecology Lab, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4PS, UK.|Marine Spatial Ecology Lab, School of Biological Sciences, University of Queensland, St. Lucia, Qld, 4072, Australia.
Peter J
PJ
Mumby
School of Marine Science and Technology, Newcastle University, Newcastle, NE1 7RU, UK.
Nicholas V C
NV
Polunin
D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D044822:Biodiversity; D057894:Coral Reefs; D005399:Fishes / Q000502:physiology*; D009427:Netherlands Antilles; D011156:Population Density; D011647:Puerto Rico; D019436:Saint Vincent and the Grenadines
biodiversity; conservation; degradation; relief; topography