Effects of Seasonal Upwelling on Inorganic and Organic Matter Dynamics in the Water Column of Eastern Pacific Coral Reefs

Abstract

The Gulf of Papagayo at the northern Pacific coast of Costa Rica experiences pronounced seasonal changes in water parameters caused by wind-driven coastal upwelling. While remote sensing and open water sampling already described the physical nature of this upwelling, the spatial and temporal effects on key parameters and processes in the water column have not been investigated yet, although being highly relevant for coral reef functioning. The present study investigated a range of water parameters on two coral reefs with different exposure to upwelling (Matapalo and Bajo Rojo) in a weekly to monthly resolution over one year (May 2013 to April 2014). Based on air temperature, wind speed and water temperature, three time clusters were defined: a) May to November 2013 without upwelling, b) December 2013 to April 2014 with moderate upwelling, punctuated by c) extreme upwelling events in February, March and April 2014. During upwelling peaks, water temperatures decreased by 7°C (Matapalo) and 9°C (Bajo Rojo) to minima of 20.1 and 15.3°C respectively, while phosphate, ammonia and nitrate concentrations increased 3 to 15-fold to maxima of 1.3 μmol PO4 3- L-1, 3.0 μmol NH4 + L-1 and 9.7 μmol NO3 - L-1. This increased availability of nutrients triggered several successive phytoplankton blooms as indicated by 3- (Matapalo) and 6-fold (Bajo Rojo) increases in chlorophyll a concentrations. Particulate organic carbon and nitrogen (POC and PON) increased by 40 and 70% respectively from February to April 2014. Dissolved organic carbon (DOC) increased by 70% in December and stayed elevated for at least 4 months, indicating high organic matter release by primary producers. Such strong cascading effects of upwelling on organic matter dynamics on coral reefs have not been reported previously, although likely impacting many reefs in comparable upwelling systems.

Microbial signatures of protected and impacted Northern Caribbean reefs: changes from Cuba to the Florida Keys

“…However, future studies would benefit from collecting samples at a higher spatial or temporal resolution in order to unravel the process of microbialization on reefs. Additionally, there are other examples of reefs that are subjected to high loads of organic and inorganic nutrients as well as pollution, like Vardero reef in Colombia (Pizarro et al, 2017) or reefs subjected to upwelling events (Leichter et al, 2003;Stuhldreier et al, 2015). Comparisons of microbial community dynamics between these drastically different reef regimes like Vardero reef with JR would extend our knowledge of how microbial communities contribute to energy cycling and reef health.…”

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

“…Sub-samples were kept dark and frozen until the end of the study period and were analyzed for nitrate (NO ) and nitrite concentrations using a Thermo Scientific UV Evolution 201 ® photometer based on a method revised by García-Robledo, Corzo & Papaspyrou (2014) ( ; LOD (NO x ) = 0.162 µmol L −1 ). A detailed description of the temporal variability in physicochemical and organic parameters at the study site can be found in Stuhldreier et al (2015) .…”

Characterizing the ecology of coral reef microorganisms across different scales within the Caribbean

“…However, future studies would benefit from collecting samples at a higher spatial or temporal resolution in order to unravel the process of microbialization on reefs. Additionally, there are other examples of reefs that are subjected to high loads of organic and inorganic nutrients as well as pollution, like Vardero reef in Colombia (Pizarro et al 2017) or reefs subjected to upwelling events (Leichter et al 2003;Stuhldreier et al 2015). Comparisons of microbial community dynamics between these drastically different reef regimes like Vardero reef with Jardines de la…”