Water Quality and Herbivory Interactively Drive Coral-Reef Recovery Patterns in American Samoa

Abstract

BackgroundCompared with a wealth of information regarding coral-reef recovery patterns following major disturbances, less insight exists to explain the cause(s) of spatial variation in the recovery process.Methodology/Principal FindingsThis study quantifies the influence of herbivory and water quality upon coral reef assemblages through space and time in Tutuila, American Samoa, a Pacific high island. Widespread declines in dominant corals (Acropora and Montipora) resulted from cyclone Heta at the end of 2003, shortly after the study began. Four sites that initially had similar coral reef assemblages but differential temporal dynamics four years following the disturbance event were classified by standardized measures of ‘recovery status’, defined by rates of change in ecological measures that are known to be sensitive to localized stressors. Status was best predicted, interactively, by water quality and herbivory. Expanding upon temporal trends, this study examined if similar dependencies existed through space; building multiple regression models to identify linkages between similar status measures and local stressors for 17 localities around Tutuila. The results highlighted consistent, interactive interdependencies for coral reef assemblages residing upon two unique geological reef types. Finally, the predictive regression models produced at the island scale were graphically interpreted with respect to hypothesized site-specific recovery thresholds.Conclusions/SignificanceCumulatively, our study purports that moving away from describing relatively well-known patterns behind recovery, and focusing upon understanding causes, improves our foundation to predict future ecological dynamics, and thus improves coral reef management.

Effects of simulated eutrophication and overfishing on algae and invertebrate settlement in a coral reef of Koh Phangan, Gulf of Thailand

“…While a limited number of previous studies showed that nutrients can drive macroalgal production in some locations (Smith et al 2001;Lapointe et al 2004;Littler et al, 2006a), the majority of field experiments identified herbivory as the key controlling factor for algal growth (Miller et al 1999;Thacker et al 2001;Belliveau and Paul 2002;Diaz-Pulido and McCook 2003;McClanahan et al 2003;Sotka and Hay 2009;Burkepile and Hay 2009;Rasher et al 2012;. The conflicting results from field experiments may be due to complex interactions between herbivory and nutrients that may vary with productivity, latitude, algal group and duration of study (Burkepile and Hay 2006;Houk et al 2010;Smith et al 2010).…”

“…Available studies have rarely assessed the importance of these controls on reefs with varying levels of anthropogenic influence (Rasher et al 2012). However, such studies are needed to better evaluate the context dependency of bottom-up versus top-down effects (Houk et al 2010;Smith et al 2010).…”

Global Gradients of Coral Exposure to Environmental Stresses and Implications for Local Management

“…There are limited insights for identifying when thresholds may be crossed, in a setting with interactive, and cumulative impacts of multiple stressors, which often result in spurious and confounding effects [2], [24]. In addition, a system's response to stressors can adopt various linear and non-linear complex behaviour patterns, which for modelling purposes can be represented in many forms of fuzzy logic membership functions including trapezoidal, sinusoidal, logistic, Gaussian etc [2], [48].…”

Commercial coral-reef fisheries across Micronesia: A need for improving management

“…While self-reinforcing mechanisms are driving harvest volumes up, many desirable reef fish are known to have slow growth and late reproductive maturation (Choat et al 1996;Birkeland 2004;Heupel et al 2010). The consequences of ensuing fishery depletions include reduced ecological functions and altered trophic structures that threaten coral-reef integrity and resilience (Folke et al 2004;Cinner and McClanahan 2006;Houk et al 2010), as well as social structure (Costanza et al 1997;Brander et al 2007).…”