Dynamics in benthic community composition and influencing factors in an upwelling-exposed coral reef on the Pacific coast of Costa Rica

Abstract

Seasonal upwelling at the northern Pacific coast of Costa Rica offers the opportunity to investigate the effects of pronounced changes in key water parameters on fine-scale dynamics of local coral reef communities. This study monitored benthic community composition at Matapalo reef (10.539°N, 85.766°W) by weekly observations of permanent benthic quadrats from April 2013 to April 2014. Monitoring was accompanied by surveys of herbivore abundance and biomass and measurements of water temperature and inorganic nutrient concentrations. Findings revealed that the reef-building corals Pocillopora spp. exhibited an exceptional rapid increase from 22 to 51% relative benthic cover. By contrast, turf algae cover decreased from 63 to 24%, resulting in a corresponding increase in crustose coralline algae cover. The macroalga Caulerpa sertularioides covered up to 15% of the reef in April 2013, disappeared after synchronized gamete release in May, and subsequently exhibited slow regrowth. Parallel monitoring of influencing factors suggest that C. sertularioides cover was mainly regulated by their reproductive cycle, while that of turf algae was likely controlled by high abundances of herbivores. Upwelling events in February and March 2014 decreased mean daily seawater temperatures by up to 7 °C and increased nutrient concentrations up to 5- (phosphate) and 16-fold (nitrate) compared to mean values during the rest of the year. Changes in benthic community composition did not appear to correspond to the strong environmental changes, but rather shifted from turf algae to hard coral dominance over the entire year of observation. The exceptional high dynamic over the annual observation period encourages further research on the adaptation potential of coral reefs to environmental variability.

Rapid bioerosion in a tropical upwelling coral reef

“…Low seawater temperature, low dissolved oxygen concentration and enhanced nutrient concentrations provide evidence that several cold water intrusions (i.e. upwelling event) influenced the study site at Matapalo Reef during the period from December 2013 to April 2014 [ 23 , 24 ]. Data from Marina Papagayo (a field site within ~200 m distance to a coral reef) showed that increased intrusions of cold and nutrient-enriched subsurface water rised seawater p CO 2 , lowered pH and decreased Ω arag [ 37 , 39 ].…”

“…The production of CaCO 3 by these organisms may be especially important for the reef´s CaCO 3 budget during periods with disruptive environmental events, when coral growth may cease (cf. Fig 7 , eutrophic condition; [ 24 ]). Interestingly, the observed loss in CaCO 3 substrate may explain the elevated pH and Ω arag at Matapalo Reef (i.e.…”

“…All along the ETP, continental shelf coral reef ecosystems have developed within the periphery of the optimal environmental conditions for coral growth (in respect to thermal range and turbidity). One of the larger tropical coral reefs off the Pacific coast of Costa Rica is located in the semi-sheltered Bay of Matapalo, which is part of the Gulf of Papagayo ( Fig 1 ) [ 23 , 24 ].…”

“…During this period, wind-driven upwelling and the seasonal extension of the Costa Rica Dome brings cool (22–26°C), low pH (<8), and nutrient-rich subsurface water into the Gulf of Papagayo [ 28 , 29 ]. Consequently these conditions allow the formation of extensive but poorly developed reefs [ 24 ]. In these reefs, bioerosion is an integral part of the reef framework and carbonate sediment production [ 30 , 31 ].…”

Benthic community structure on coral reefs exposed to intensive recreational snorkeling

“…palmata (the 14 most common stony coral species in Akumal Bay, as indicated by preliminary observations), or grouped as other stony coral species (identified using [ 54 ]). Macroalgae were identified as belonging to 4 growth forms: crustose coralline algae (CCA), erect calcified macroalgae (CMA), erect fleshy macroalgae (FMA), or turf algae [ 55 ]. Other sessile organisms were classified in 5 groups: gorgonians (including soft corals and sea fans), fire corals (defined as hydrocorals in the genus Millepora ), sponges, sea anemones, or zoanthids (zoantharians) [ 55 , 56 ].…”