Impact of El Niño 2015-2016 on the coral reefs of the Pacific of Costa Rica: the potential role of marine protection

Introduction: El Niño 2015-2016 was considered one of the most severe worldwide, causing the third global event of coral bleaching. Previous high-intensity El Niño events (1982-83 and 1997-98) caused high coral mortalities and deterioration of coral reef structures along the Eastern Tropical Pacific, affecting both ecosystem and associated economical activities. Objective: The aim of this study was to determine the impact of the most recent El Niño event on coral reefs from Cocos Island and the Pacific coast of southern Costa Rica. Methods: Coral reefs were surveyed before (2013-2014) and after (2016) the disturbance, using underwater visual censuses within belt transects, to quantify the bottom coverage at different depths. Results: In general, average live coral cover decreased 50% after the 2015-2016 El Niño event, with Golfo Dulce being the most affected area with 75% of live coral cover decline. However, in certain localities such as Isla del Coco and Isla del Caño, the effects of El Niño were apparently minimal, since no substantial loss of live coral cover was detected. Differences in the level of deterioration found between coral reefs could be related to several factors, including the age of the protected area, the distance to centers of human population, and the effectiveness in the application of management strategies. Conclusions: The synergistic impact of the 2015-16 El Niño event and other stressors (e.g. illegal fishing and unregulated coastal human development) increased the levels of disturbance on coral reefs, threatening their structure and functioning. It is necessary to strengthen conservation strategies in order to improve the resilience of coral reefs to the impact of natural and anthropogenic disturbances. Concrete actions such as coral reef restoration, marine environmental education, and marine spatial planning must become important tools to maintain the good health of coral reefs and ensure the sustainability of the goods and services provided by these ecosystems.

Introducción: El fenómeno El Niño del 2015-2016 fue considerado como uno de los más severos a nivel mundial, causando el tercer evento global de blanqueamiento coralino. Eventos previos de alta intensidad (1982-83 y 1997-98), causaron altas mortalidades coralinas y el deterioro de estructuras arrecifales a lo largo de Pacífico Tropical Oriental, afectando tanto al ecosistema como las actividades económicas asociadas. Objetivo: El objetivo de este estudio, fue determinar el impacto del evento El Niño 2015-2016 en la salud de los arrecifes coralinos de la Isla del Coco y la costa Pacífico Sur de Costa Rica. Métodos: La evaluación de los arrecifes de coral se realizó antes (2013-2014) y después (2016) de la perturbación, utilizando censos visuales subacuáticos en transectos de banda, con el fin de cuantificar la cobertura del fondo a distintas profundidades. Resultados: En general, la cobertura coralina viva promedio disminuyó 50% después del evento El Niño 2015-2016, siendo Golfo Dulce la zona más afectada con una reducción del 75%. Sin embargo, en ciertas localidades como las islas Coco y Caño, los efectos de El Niño fueron aparentemente mínimos, ya que no se detectó una pérdida sustancial de la cobertura coralina viva. Las diferencias en el nivel de deterioro encontradas entre los arrecifes podrían estar relacionadas con varios factores, incluyendo el tiempo transcurrido desde que se estableció el área protegida, la distancia a los centros de la población humana y la efectividad en la aplicación de estrategias de manejo. Conclusiones: El impacto sinérgico del evento El Niño 2015-2016 y otros factores de estrés (por ejemplo, la pesca ilegal y el desarrollo costero no regulado) incrementó los niveles de perturbación en los arrecifes coralinos, amenazando su estructura y funcionamiento. Es necesario fortalecer las estrategias de conservación para mejorar la resiliencia de los arrecifes coralinos ante el impacto de perturbaciones naturales y antropogénicas. Acciones concretas como la jardinería de corales, la educación ambiental marina y el ordenamiento espacial marino, deben convertirse en herramientas importantes para mantener la buena salud de los arrecifes coralinos y asegurar la sostenibilidad de los bienes y servicios proporcionados por estos ecosistemas.

Rapid bioerosion in a tropical upwelling coral reef.

Coral reefs persist in an accretion-erosion balance, which is critical for understanding the natural variability of sediment production, reef accretion, and their effects on the carbonate budget. Bioerosion (i.e. biodegradation of substrate) and encrustation (i.e. calcified overgrowth on substrate) influence the carbonate budget and the ecological functions of coral reefs, by substrate formation/consolidation/erosion, food availability and nutrient cycling. This study investigates settlement succession and carbonate budget change by bioeroding and encrusting calcifying organisms on experimentally deployed coral substrates (skeletal fragments of Stylophora pistillata branches). The substrates were deployed in a marginal coral reef located in the Gulf of Papagayo (Costa Rica, Eastern Tropical Pacific) for four months during the northern winter upwelling period (December 2013 to March 2014), and consecutively sampled after each month. Due to the upwelling environmental conditions within the Eastern Tropical Pacific, this region serves as a natural laboratory to study ecological processes such as bioerosion, which may reflect climate change scenarios. Time-series analyses showed a rapid settlement of bioeroders, particularly of lithophagine bivalves of the genus Lithophaga/Leiosolenus (Dillwyn, 1817), within the first two months of exposure. The observed enhanced calcium carbonate loss of coral substrate (>30%) may influence seawater carbon chemistry. This is evident by measurements of an elevated seawater pH (>8.2) and aragonite saturation state (Ωarag >3) at Matapalo Reef during the upwelling period, when compared to a previous upwelling event observed at a nearby site in distance to a coral reef (Marina Papagayo). Due to the resulting local carbonate buffer effect of the seawater, an influx of atmospheric CO2 into reef waters was observed. Substrates showed no secondary cements in thin-section analyses, despite constant seawater carbonate oversaturation (Ωarag >2.8) during the field experiment. Micro Computerized Tomography (µCT) scans and microcast-embeddings of the substrates revealed that the carbonate loss was primarily due to internal macrobioerosion and an increase in microbioerosion. This study emphasizes the interconnected effects of upwelling and carbonate bioerosion on the reef carbonate budget and the ecological turnovers of carbonate producers in tropical coral reefs under environmental change.

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

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.

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

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 PO43- 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.

Clima y temperatura sub-superficial del mar en Bahía Culebra, Golfo de Papagayo, Costa Rica / Climate and subsurface sea temperature in Bahía Culebra, Costa Rica

Climate and subsurface sea temperature in Bahía Culebra, Costa Rica. Bahía Culebra, Golfo de Papagayo, Costa Rica is a seasonal upwelling area. To determine the relationship of climate and the subsurface temperature variability at Bahía Culebra, we analyzed nine records of sea subsurface temperature from the Bay, continuously recorded from 1998 to 2010. The analysis characterized the annual cycle and explored the influence of different climate variability sources on the subsurface sea temperature and air temperature recorded in Bahía Culebra. Data from an automatic meteorological station in the bay were studied, obtaining the annual and daily cycle for air surface temperature and wind speed. Sea surface temperature (SST) trend from 1854 to 2011 was calculated from reanalysis for the region that coverts 9-11°N, 85-87°W. Because of the positive SST trend identified in this region, results showed that annual and daily cycles in Bahía Culebra should be studied under a warming scenario since 1854, that is coherent with the global warming results and its climate variability is influenced by El Niño-Southern Oscillation (ENSO) in the Equatorial Pacific and by atmospheric forcing triggered by climate variability with Atlantic Ocean origin, because warm (cold) events in Bahía Culebra tend to occur in concordance with positive & negative (negative & positive) anomalies in Niño 3.4 (NAO) index.

Bahía Culebra, Golfo de Papagayo, Costa Rica es una región de afloramiento estacional. Para determinar la relación entre el clima y la variabilidad de la temperatura sub-superficial, se analizaron los registros de la temperatura sub-superficial del mar de nueve estaciones localizadas en la Bahía. El análisis permitió caracterizar su ciclo anual y explorar su relación con fuentes de variabilidad climática que influencian el clima regional para el periodo 1998-2010. Los resultados se contextualizaron usando además los datos de una estación meteorológica automática que funcionó en la bahía junto con el registro de la temperatura superficial del mar para una rejilla que cubre la región de 9-11°N, 85-87°W, para el periodo 1854-2011. Debido a la tendencia positiva encontrada en la región para la temperatura superficial del mar, se concluye que los resultados mostrados asociados a los ciclos anuales y diarios en Bahía Culebra deben ser interpretados bajo un escenario de cambio climático, asociado a un calentamiento ocurrido desde 1854, además coherente con lo observado globalmente, y que su variabilidad climática está influenciada no sólo por aquella ligada a la de El Niño-Oscilación del Sur, en el Pacífico Ecuatorial, sino también por influencias de tipo atmosférico relacionadas con la variabilidad en el Océano Atlántico, debido a que los eventos cálidos (fríos) en Bahía Culebra tienden a ocurrir en concordancia con anomalías positivas y negativas (negativas y positivas) de los índices Niño 3.4 y OAN, respectivamente.

Entre historias y culebras: más que una bahía (Bahía Culebra, Guanacaste, Costa Rica) / Among stories and snakes: more than a bay (Bahía Culebra, Guanacaste, Costa Rica)

Among stories and snakes: more than a bay (Bahía Culebra, Guanacaste, Costa Rica). Bahía Culebra (Culebra Bay) is a semi-closed and protected geomorphological unit, which has a wide diversity of natural resources, encouraging the settlement of human populations and consequent coastal development. Bahía Culebra has been an important place from the historical, political, cultural and economic perspective, according to the literature search which included documents dating from the mid nineteenth century until 2011, from the National Archive of Costa Rica, the National Library, the Historical Research Center in Central America and some private collections. Its beauty, road networks, and the proximity to an international airport has made easier for it to become an intensive tourism development center. Coastal development was accelerated by the creation of the Polo Turístico Golfo de Papagayo (Papagayo Gulf Tourist Destination project). It should strengthen the legal framework and implementation of actions to promote the welfare of local populations and the proper management of natural resources, taking into account all factors and actors involved.

Bahía Culebra (Golfo de Papagayo, Guanacaste, Costa Rica) es una unidad geomorfológica semicerrada y bastante protegida, que cuenta con una amplia diversidad de recursos naturales, favoreciendo el asentamiento de poblaciones humanas y su consecuente desarrollo marinocostero. La reseña histórica de Bahía Culebra indica que este ha sido un sitio muy importante desde la perspectiva histórica, política, cultural y económica. La consulta bibliográfica incluyó documentos que datan de mediados del siglo XIX hasta el año 2011, los cuales fueron recopilados del Archivo Nacional de Costa Rica, la Biblioteca Nacional, el Centro de Documentación del Centro de Investigaciones Históricas de América Central y algunas colecciones privadas. Su notoria belleza escénica, la disponibilidad de redes viales en buen estado y la cercanía a un aeropuerto internacional han facilitado que la bahía se convierta en un centro turístico intensivo, generando un acelerado desarrollo costero a raíz de la creación del proyecto Polo Turístico Golfo de Papagayo (PTGP). Se debe fortalecer el marco jurídico e implementar acciones que promuevan el bienestar de las poblaciones locales y la adecuada gestión de los recursos naturales, tomando en cuenta todos los factores y actores involucrados.