The Physical Environment in Coral Reefs of the Tayrona National Natural Park (Colombian Caribbean) in Response to Seasonal Upwelling

Abstract

Coral reefs are subjected to physical changes in their surroundings including wind velocity, water temperature, and water currents that can affect ecological processes on different spatial and temporal scales. However, the dynamics of these physical variables in coral reef ecosystems are poorly understood. In this context, Tayrona National Natural Park (TNNP) in the Colombian Caribbean is an ideal study location because it contains coral reefs and is exposed to seasonal upwelling that strongly changes all key physical factors mentioned above. This study therefore investigated wind velocity and water temperature over two years, as well as water current velocity and direction for representative months of each season at a windand wave-exposed and a sheltered coral reef site in one exemplary bay of TNNP using meteorological data, temperature loggers, and an Acoustic Doppler Current Profiler (ADCP) in order to describe the spatiotemporal variations of the physical environment. Findings revealed that water temperatures (28.7 ± 0.8 °C and maximal 30.3 °C during non-upwelling; 25.1 ± 1.7 °C and minimal 20.3 °C during upwelling) exhibited no significant differences between sites and were negatively correlated with wind velocities (0.4 ± 0.3 m s -1 during non-upwelling and 1.8 ± 1.0 m s -1 with a maximum of 4.1 m s -1 during upwelling). Water current velocity was significantly higher at the exposed compared to the sheltered site during non-upwelling periods at a water depth of 8-10 m. During upwelling, water current velocities were also higher at the exposed site (6.4 cm s -1 exposed and 5.9 cm s -1 sheltered), but when wind speed surpassed 1.7 m s -1, no spatial differences occurred. Water currents showed a clockwise circulation during upwelling following the wind fields, but no clear circulation pattern during non-upwelling. Significant positive correlation between wind and water current velocity was detected at the sheltered, but not at the exposed site. Wind-stress at the exposed site affected water currents throughout the entire water column (at least 10 m deep) during both seasons, but reached only until 3-4 m water depth at the sheltered site during non-upwelling and down to 10 m during upwelling. Consequently, organisms at the exposed site experience constantly high water current exposure throughout the year. This may explain the pronounced site-specific reef community composition differences as water current velocity and circulation control distribution of invertebrate larvae and supply with plankton and essential nutrients. KEYWORDS: RESUMENEl entorno físico en arrecifes coralinos del Parque Nacional Natural Tayrona (Caribe colombiano) en respuesta a la surgencia estacional. Los arrecifes de coral están sujetos a cambios físicos en su entorno, tales como velocidad del viento, temperatura del agua y corrientes marinas, que pueden llegar a afectar los procesos ecológicos en diferentes escalas espaciales y temporales. Sin embargo, es poco lo que se conoce sobre la dinámica de las variables físicas en lo...

Multi-scale processes drive benthic community structure in upwelling-affected coral reefs

“…However, given the calculated wave exposure for the investigated sites, hydrodynamic regimes differ from bay to bay as suggested by Garzón-Ferreira and Cano (1991) and exhibit site-specific temporal variations as shown by Bayraktarov et al (2014b). Additional community assessments along the hydrodynamic gradient within the bays of TNNP could elucidate the effects of hydrodynamics on local benthic communities as proposed for coral assemblages by Werding and Sánchez (1989).…”

“…Sediment transport and accumulation are generally correlated with hydrodynamics, as shown for a Hawaiian fringing reef where wave energy and water currents control sediment resuspension and transport (Ogston et al, 2004). Differences in sand coverage between sheltered and exposed sites in TNNP bays are therefore likely due to generally higher wave energy and water current velocities at exposed sites (Bayraktarov et al, 2014b), resuspending sediments and transporting resuspended material to sheltered or deeper parts where it accumulates . Our findings are in accordance with former studies, stating that sand abundance is inversely correlated with wave exposure (Bradbury and Young, 1981;Graus and Macintyre, 1989;Roberts et al, 1992).…”

“…However, none of the quantified water parameters showed significant intra-bay differences ( Table 2; see also Bayraktarov et al, 2014b). On the contrary, similar topographic conditions among the bays in TNNP (Table 1, Figure 1) cause comparable gradients in wave exposure within the bays ( Table 1; Werding and Sánchez, 1989;Garzón-Ferreira and Cano, 1991).…”

“…During this period (hereafter referred to as upwelling season), strong wind-induced water currents and wave action prevail, mean monthly water temperatures decrease to around 25 • C with minimal water temperatures being as low as 20 • C, and salinity as well as nutrient availability increase (Bayraktarov et al, 2014a). During the major rainy season from September to November (hereafter referred to as non-upwelling season), trade winds cease and surface water temperatures increase (monthly means around 28 • C; maximum values greater than 30 • C, Salzwedel and Müller, 1983;Bayraktarov et al, 2014b). During this period, increased precipitation and terrestrial run-off may result in higher turbidity and lower salinity (Salzwedel and Müller, 1983;Diaz-Pulido and Garzón-Ferreira, 2002).…”

“…In addition, environmental changes also influence primary production of major benthic photoautotrophs (Eidens et al, 2014), thereby affecting benthic community composition. Other factors that potentially influence benthic communities in the area include wave exposure, substrate availability, and changes in light intensity (Antonius, 1972;Erhardt, 1975;Werding and Sánchez, 1989;Garzón-Ferreira, 1998;Vega-Sequeda et al, 2008;Bayraktarov et al, 2014b).…”