Abstract
Previous work has highlighted the critical role of macroalgal productivity and dynamics in supporting and structuring marine food webs. Spatio-temporal variability in macroalgae can alter coastal ecosystems, a relationship particularly visible along upwelling-influenced coastlines. As a result of its equatorial location and nutrient rich, upwelling-influenced waters, the Galápagos Archipelago in the East Pacific, hosts a productive and biodiverse marine ecosystem. Reports and collections of macroalgae date back to the Beagle voyage, and since then, more than three hundred species have been reported. However, their ecology and functional role in the ecosystem is not well understood. According to various disparate and in part anecdotal sources of information, abundant and diverse communities exist in the Western regions of the archipelago, the North is essentially barren, and in the central/South abundance and distribution is variable and less well defined. Both oceanographic conditions and herbivore influence have been theorized to cause this pattern. Extensive changes in macroalgal productivity and community composition have occurred during strong ENSO events, and subsequent declines in marine iguana (an endemic and iconic grazer) populations have been linked to these changes. Iguanas are only one species of a diverse and abundant group of marine grazers in the system, highlighting the potentially important role of macroalgal productivity in the marine food web. This review represents a first compilation and discussion of the available literature and presents topics for future research.
Highlights
Marine macroalgae, or seaweeds as they are commonly known, are an important source of marine primary productivity, and provide a range of ecosystem services (Mann, 1973; Dayton, 1985)
Macroalgae exist in the archipelago, and the most exhaustive investigations of Galápagos macroalgae have been taxonomic in nature
This review offers a compilation and discussion of relevant literature-an attempt to summarize and integrate available knowledge-so that gaps in understanding of Galápagos macroalgal ecology may be identified as areas for future research
Summary
Seaweeds as they are commonly known, are an important source of marine primary productivity, and provide a range of ecosystem services (Mann, 1973; Dayton, 1985). Global trends exhibit a propensity for diverse and abundant macroalgal communities to flourish in relatively cold, nutrient rich waters (higher latitudes), while entirely different and relatively species-poor assemblages of species inhabit warm and generally nutrientlimited tropical waters (Schils & Coppejans, 2003a; Kerswell, 2006). This general pattern is confounded by smaller-scale physical and biological factors, such as tropical upwelling, anthropogenic nutrient pulses, and localized overabundances of grazers (Bell, 1992; Lobban & Harrison, 1997). Work in other upwelling influenced areas has revealed oceanographic and herbivore related biogeographic patterns in macroalgal community compositions and biomasses, with diversity and abundances related positively to upwelling (colder, nutrient rich waters) influence, and negatively to grazer (urchin) abundances (Bustamante & Branch, 1996; Schils & Coppejans, 2003a; Sangil, Sansón, & Afonso-Carrillo, 2011)
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