The Impacts of Red Mangrove (rhizophora Mangle) Deforestation on Zooplankton Communities in Bocas Del Toro, Panama

Deforestation impact studies have generally focused on tropical rainforests or temperate coniferous woodlands. However, extensive clear-cutting is currently occurring in a wide-ranging, but far less recognized habitat: the world's mangrove forests. These coastal forests thrive in areas of low wave action and high sediment availability, where mangrove trees develop dense and productive ecosystems (Alongi, 2002). Extensive aerial and subtidal prop root networks, a dense canopy, and varying water conditions allow these forests to support unique assemblages of flora and fauna. Even as mangrove deforestation continues to alter coastlines, these forests are increasingly recognized as important nursery habitats and feeding grounds for many larval, juvenile and adult fish and invertebrate species (e.g., Nagelkerken et al., 2001, 2002; Mumby et al., 2004; Nagelkerken and van der Velde, 2004). Larval populations of a wide variety of marine species recruit to these sheltered, structurally complex, shaded and nutrient-rich ecosystems (Krishnamurthy, 1982; Dennis, 1992). Whether zooplankton communities differ between intact and cleared mangrove areas is unknown. Structural complexity should affect flow and hence food availability and larval retention rates. However, results from different systems are inconsistent. In kelp forests, structural complexity inhibits deposition of suspended particles, possibly reducing food availability for benthic organisms and retarding zooplankton dispersal (Eckman et al., 1989). As with inhibited flow in kelp forests, Toffart (1983) suggests that there is a rapid decrease in species diversity from the seaward edge of a mangrove forest towards the shore because of reduced flow. This would particularly affect less active swimmers. However, few direct measurements of zooplankton inside and outside mangroves exist (e.g., Ambler et al., 1991). Mangroves may be preferred settlement sites for some highly mobile species that can actively select this habitat. Capacity for swift directional travel among zooplankton (Luckenbach and Orth, 1992; Ferrari et al., 2003) may allow these species to actively select mangrove habitat over less complex, more open environments (i.e., cleared mangrove areas). Low flow in mangroves may increase (or decrease) zooplankton abundance and create retention zones where zooplankton can develop near suitable adult habitat (Paula et al., 2004). Zooplankton survival may be high in mangroves due to favorable substrate and increased niches (due to root complexity), greater food availability, and reduced predation (Laegdsgaard and Johnson, 1995; Cocheret de la Moriniere et al., 2004). The dense mangrove root networks retain nutrients and sediments carried in runoff from adjacent land or produced in situ, having the dual effect of fueling productivity (Bouillon et al., 2000) and creating murky water conditions, reducing visibility for predators. The structural complexity of mangrove roots may provide settling larvae with shelter from predators and open water currents. On the other hand, differences in structural complexity within man-