Ecological Linkages in a Caribbean Estuary Bay
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Vol. 533: 29–46, 2015 MARINE ECOLOGY PROGRESS SERIES Published August 6 doi: 10.3354/meps11342 Mar Ecol Prog Ser Ecological linkages in a Caribbean estuary bay H. Andrade1,2,*, J. Santos1, M. J. Ixquiac3 1Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway 2Akvaplan-niva AS, Framsenteret, 9296 Tromsø, Norway 3Centro de Estudios del Mar y Acuicultura, Universidad de San Carlos de Guatemala, Guatemala 01012, Guatemala ABSTRACT: Central America and the western Caribbean regions form a center of freshwater and marine biodiversity that is increasingly becoming the focus of ecological and evolutionary studies. We conducted an integrated ecological study of Amatique Bay, Guatemala, a major estuary la goon connected to the low-lying Lake Izabal and to the Mesoamerican Reef System, and provide novel information for the management and conservation of similar systems across the Caribbean. Precip- itation and wind regimes constitute important environmental drivers of ecosystem functioning, which partially compensate for the weak tidal-forcing that is characteristic of the Caribbean Sea. Seasonal peaks in temperature and precipitation were strongly correlated to the reproduction of marine, catadromous and estuarine fish species, suggesting that the ensuing increase in primary production provides larval fish with an abundant food source. Increased abundances of transient marine species were observed during the dry season, which may be explained by passive transport, feeding migration, or both, considering that prey may be more abundant inshore and that environmental conditions are dominated by higher salinity and stronger onshore winds during this period. Despite being a stopover site for many long-range migrating shorebird species, the Bay serves primarily as a resting place since it lacks extensive tides and tidal flats, and thus provides limited access to invertebrate prey. Furthermore, this sheltered environment, featuring abundant freshwater, seasonally high water clarity, and low tidal amplitude, is likely to provide good habitat for abundant seagrasses and manatees. The Lake Izabal-Amatique Bay complex demonstrates a wide range of teleconnections and connectivity among terrestrial, freshwater, and marine oceanic and reef ecosystems. Understanding the evolution and ecology underlying this highly connected system is required for the management of the multi-trophic, small-scale fisheries it sustains. KEY WORDS: Fisheries · Migratory shorebirds · Manatee · Life history · Environmental drivers · Tropical conservation · Evolution · Central America Resale or republication not permitted without written consent of the publisher INTRODUCTION water ecosystems by marine species (i.e. killifishes, cichlids) played a major role after a sequence of salt- The western Caribbean is highly diverse across ter- water intrusions and regressions (Hulsey & López- restrial, marine and freshwater realms, but there is a Fernández 2011). In the marine realm, the Caribbean limited understanding of linkages between its coastal Province has historically been the center of ecological assemblages of fish, birds, and mammals across these speciation and radiation of fish and many inver - systems. The paleontological and phylogenetic re - tebrate groups in the Atlantic, producing and export- cords suggest that the Central American region was ing species. but also accumulating biodiversity pro- at the core of an explosive radiation of freshwater fish duced in peripheral habitats (Briggs & Bowen 2012, species (Briggs 1984, Chakrabarty & Albert 2011). Bowen et al. 2013). The Caribbean province was also Part of the taxa were secondary freshwater fish origi- once an area of sirenian (manatee, sea cow) radiation. nally from South America, but the invasion of fresh- However, the closure of the Central American Sea - *Corresponding author: [email protected] © Inter-Research 2015 · www.int-res.com 30 Mar Ecol Prog Ser 533: 29–46, 2015 way in the Pliocene (ca. 3 million yr ago) resulted in The estuarine areas of Central America and the mass extinctions of seagrasses and sirenian species, Caribbean are important for both conservation and and only a single species, the manatee Trichechus human utilization, especially considering their signif- manatus remains (Hunter et al. 2012, Velez-Juarbe et icance as a stop-over for long distance migrants (e.g. al. 2012, Benoit et al. 2013). The rise of the Isthmus of shorebirds), seasonal habitat for short-range Panama prompted the migration of forest birds pre- migrants, and habitat for resident taxa (Faaborg et al. dominantly in the direction south to north, which pre- 2010, Latta 2012, Somveille et al. 2013). Amatique sumably led to the high levels of bird diversity also Bay in Guatemala is connected by freshwater runoff observed in this region. For shorebirds (Order to the Mesoamerican reef, the largest barrier reef in Charadriiformes), however, understanding of their the Western Hemisphere (Soto et al. 2009), and is a original migratory behavior and home range is prob- typical Caribbean estuarine ecosystem. Upstream lematic (Weir et al. 2009, Livezey 2010, Zink 2011). (40 km) from the Bay, the low-lying Lake Izabal Many extant Arctic Charadriiformes are long-range forms the southern boundary of the Usumacinta fish migrants with northern breeding grounds, but which faunal province, a region characterized by a highly overwinter in the southern hemisphere. However, diverse continental ichthyofauna. The Bay may have several lineages of shorebirds from the southern been a major route of incursion of marine species into hemisphere are predominantly residents or short- the freshwater assemblages of Central America range migrants. Thus, the present assemblages of (Hulsey & López-Fernández 2011). To conserve this aquatic and wetland fauna are resultant of a complex complex, natural protected areas have been imple- of freshwater and marine radiations and transgres- mented across the watershed, including 2 Ramsar sions, as well as colonization by continental species. wetland sites of international importance: the Río The lack of studies examining coastal species assem- Sarstún Multiple Reserve Zone, and Punta de Man- blages and their functions, particularly in Neotropical abique Wildlife Refuge (Fig. 1). Punta de Manabique estuaries, hampers the understanding of ecological alone shelters more than 450 plant species, and 810 processes that may have driven the evolution of many faunal taxa (Jolón-Morales 2006). Several threatened taxa (Sheaves & Johnston 2009, Barletta et al. 2010, or vulnerable migratory species, including the mana- Atwood et al. 2012). tee, contribute to this biodiversity. Agriculture, herd- Punta de Manabique Sarstún River Amatique Bay La Graciosa Bay Livingston 15°48' N Puerto Barrios Dulce River Santo Tomás Protected areas Lake Izabal Caribbean Sea 15°24' 89°53'W 88°36' Fig. 1. Map of Amatique Bay and current protected areas (dark grey). Punta de Manabique Wildlife Refuge includes a protected marine zone Andrade et al.: Ecological linkages in an estuary bay 31 ing and forestry, activities that are often preceded by of the Bay as well as in the rivers draining into it slashing and burning of existing vegetation, have (Hernández et al. 2012). The dominant species is the been identified as major sources of impact on the red mangrove Rhizophora mangle, but Avicennia wetland habitat in this area (Yañez-Arancibia et al. germinans, Laguncularia racemosa and Conocarpus 1999). However, the presence of 2 harbors receiving erectus are also common (Yañez-Arancibia et al. an excess of 1200 ships annually may also have a 1994). Seagrass beds, which are particularly abun- negative influence on the aquatic communities (Abt dant in La Graciosa Bay, cover approx. 38 km2, and 6 Associates/Woods Hole Group 2003). Fishing pres- species have been identified to date, with Thalassia sure is also high and landings account for nearly 60% testudinum as the dominant species (Yañez-Aran- of the economic value generated by fishing in the cibia et al. 1994, Arrivillaga & Baltz 1999, MacDon- Guatemalan Caribbean, supporting the livelihood of ald-Barrios 2011). Some reef structures exist, mainly more than 1000 harvesters (Ixquiac-Cabrera et al. around Punta de Manabique in the form of continen- 2008, Andrade & Midré 2011, Heyman & Granados- tal carbonate banks. These reefs are dominated by Dieseldorff 2012). Thus, the range of conservation, sedimentation-resistant coral species, such as Side - ecological and social interests to be accommodated is rastrea siderea. Live coral cover, however, is low, and broad and often conflicting. non-coralline macroalgae is highly abundant (Fon- In this study, we attempted to describe this Carib- seca & Arrivillaga 2003). The mud-dominated areas bean estuarine-marine complex with the goal of at the mouth of the Sarstún River give rise to the most identifying ecological drivers for ecosystem function- valuable shrimp fishery in the Gulf of Honduras ing and evolution in Neotropical estuaries. Ecological (Heyman & Kjerfve 2001). studies that integrate marine and freshwater ecosys- tems have rarely been performed in Caribbean estu- aries. Our current understanding of these systems is Collection and analysis of meteorological and derived from information that is spread across data oceanographic data reports, fisheries statistics, and very specialized pub- lications. Thus, we compiled environmental and eco- Time-series of environmental data were retrieved logical information from different