Assessing the ecological effects of human impacts on coral reefs in Bocas del Toro, Panama

Abstract

Environmental and biological reef monitoring was conducted in Almirante Bay (Bahía Almirante) in Bocas del Toro, Panama, to assess impacts from anthropogenic developments. An integrated monitoring investigated how seasonal temperature stress, turbidity, eutrophication and physical impacts threatened reef health and biodiversity throughout the region. Environmental parameters such as total suspended solids [TSS], carbon isotopes (δ(13)C), C/N ratios, chlorophyll a, irradiance, secchi depth, size fractions of the sediments and isotope composition of dissolved inorganic carbon [DIC] of the water were measured throughout the years 2010 and 2011 and were analysed in order to identify different impact sources. Compared to data from Collin et al. (Smithsonian Contributions to the Marine Sciences 38:324-334, 2009) chlorophyll a has doubled at sites close to the city and the port Almirante (from 0.46-0.49 to 0.78-0.97 μg l(-1)) and suspension load increased, visible by a decrease in secchi depth values. Visibility decreased from 9-13 m down to 4 m at the bay inlet Boca del Drago, which is strongly exposed to river run off and dredging for the shipping traffic. Eutrophication and turbidity levels seemed to be the determining factor for the loss of hard coral diversity, most significant at chlorophyll a levels higher than 0.5 μg l(-1) and TSS levels higher than 4.7 mg l(-1). Hard coral cover within the bay has also declined, at some sites down to <10 % with extremely low diversities (7 hard coral species). The hard coral species Porites furcata dominated the reefs in highly impacted areas and showed a strong recovery after bleaching and a higher tolerance to turbidity and eutrophication compared to other hard coral species in the bay. Serious overfishing was detected in the region by a lack of adult and carnivorous fish species, such as grunts, snappers and groupers. Study sites less impacted by anthropogenic activities and/or those with local protection showed a higher hard coral cover and fish abundance; however, an overall loss of hard coral diversity was observed.

Molluscan subfossil assemblages reveal the long-term deterioration of coral reef environments in Caribbean Panama

“…Our molluscan subfossil data provide the first description of historical environmental conditions for reefs in Bocas and contribute valuable information about current reef environments, as no environmental data exists for these reefs before 2000 and current monitoring continues to be limited in spatial and environmental scope (Collin et al, 2009;Seemann et al, 2014). The bivalve and gastropod communities in Bocas were typical of coral reefs with a high availability of hard substrates and relatively high productivity due to the influence of river runoff.…”

“…At lagoonal reefs, the timing of change is likely contemporaneous with the onset of extensive coastal land clearing for banana agriculture in the first half of the 20th century, while at offshore reefs, changes are contemporaneous with the introduction of large quantities of synthetic agrochemicals toxic to marine life which were applied to plantations starting in the mid-20th century (Stephens, 2008;Cramer, 2013). Declining water quality due to land-based runoff since the mid-20th century has been documented for Almirante Bay from terrestrial plant biomarkers in reef sediments (Aronson et al, 2014) and from recent small-scale monitoring studies (Collin et al, 2009;Seemann et al, 2014), but the convergence of offshore and lagoonal molluscan communities since the 1960s documented here confirms that water quality has also substantially deteriorated offshore.…”

Millennial‐scale change in the structure of a Caribbean reef ecosystem and the role of human and natural disturbance

“…4c). Although it is possible that ecosystem deterioration at Punta Donato is also related to hydrological change, the continued presence of several coral-dominated patch reefs of similar depth but in locations within Bahia Almirante less influenced by land-based runoff (Seemann et al 2014) suggests otherwise. This period of ecosystem reversion is one of relatively high human population density near Almirante Bay and increasing exploitation of coastal marine resources from indigenous inhabitants, non-local indigenous and European traders, pirates engaging in intensive harvesting of mega-herbivores including green sea turtles and manatees, and land clearing for industrial-scale banana agriculture (Araya 2004, Cramer 2013, Wake et al 2013.…”

The resilience of reef invertebrate biodiversity to coral mortality

“…), and Agariciidae is now the most abundant scleractinian coral family on mid‐depth reefs in Almirante Bay (Seeman et al. ). Against this backdrop of degradation typical of many Caribbean reefs, coral cover in Almirante Bay remained relatively high for the region (Guzman , Jackson et al.…”

“…Over the past century, some of these reefs have become increasingly turbid and nutrient-loaded due to a variety of large-scale anthropogenic disturbances, such as overfishing and landclearing for intensive banana production in the archipelago (Cramer et al 2012). As a consequence, reefs have transitioned to more stress tolerant and opportunistic species of Agaricia (Aronson et al 2004), and Agariciidae is now the most abundant scleractinian coral family on mid-depth reefs in Almirante Bay (Seeman et al 2013). Against this backdrop of degradation typical of many Caribbean reefs, coral cover in Almirante Bay remained relatively high for the region (Guzman 2003, Jackson et al 2014) until a recent mortality event associated with hypoxia that killed some Agaricia reefs (< 5% coral cover remaining) but left others relatively unscathed (>20% cover; A. Altieri, unpublished data).…”