Showing papers by "Hector M. Guzman published in 2011"

Global Human Footprint on the Linkage between Biodiversity and Ecosystem Functioning in Reef Fishes

Abstract: Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a nonsaturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world’s coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas.

Variation in reef fish and invertebrate communities with level of protection from fishing across the Eastern Tropical Pacific seascape

Abstract: Aim To quantify general differences in reef community structure between well enforced and poorly enforced marine protected areas (MPAs) and fished sites across the Eastern Tropical Pacific (ETP) regional seascape Location The Pacific continental margin and oceanic islands of Costa Rica, Panama, Colombia and Ecuador, including World Heritage sites at Galapagos, Coiba, Cocos and Malpelo Methods Densities of reef fishes, mobile and sessile invertebrates, and macroalgae were quantified using underwater visual surveys at 136 ‘no-take’ and 54 openly fished sites associated with seven large MPAs that encompassed a range of management strategies. Spatial variation inmultivariate and univariate community metrics was related to three levels of fishing pressure (high-protection MPAs, limited-protection MPAs, fishing zones) for both continental and oceanic reefs. Results High-protection MPAs possessed a much greater biomass of higher carnivorous fishes, lower densities of asteroids and Eucidaris spp. urchins, and higher coral cover than limited-protection MPAs and fished zones. These results were generally consistent with the hypothesis that overfishing of predatory fishes within the ETP has led to increased densities of habitat-modifying macroinvertebrates, which has contributed to regional declines in coral cover. Major differences in ecological patterns were also evident between continental and oceanic biogeographic provinces. Main conclusions Fishing down the food web, with associated trophic cascades, has occurred to a greater extent along the continental coast than off oceanic islands. Poorly enforced MPAs generate food webs more similar to those present in fished areas than in well-protected MPAs.

Reef coral reproduction in the eastern Pacific: Costa Rica, Panamá, and the Galápagos Islands (Ecuador). VI. Agariciidae, Pavona clavus

Abstract: The reproductive ecology of the zooxanthellate reef coral Pavona clavus was investigated at several sites in Costa Rica, Panama, and the Galapagos Islands (Ecuador) over the period 1985–2009. Pavona clavus displayed stable gonochorism as only five hermaphrodites were found in 590 samples. At four of five locations, sex ratios were skewed toward female dominance; however, at Saboga Island (Panama) male colonies predominated. In Panama, sexual maturity was observed in an estimated eight-year-old female colony, and several colonies of 10–20 years of age demonstrated gametogenesis. Sexual activity was observed at all study sites, but gamete development occurred in only 14–31% of colonies sampled sporadically. Seasonality of gametogenic activity occurred predominantly during the warm/wet season, June to August, at mainland sites (Cano Island, Costa Rica, and Gulfs of Chiriqui and Panama, Panama). This pattern was repeated in the Galapagos Islands, but mainly from March to May when seasonally high sea temperatures and rainfall prevailed there. Histological sampling and field observations indicated that spawning was centered around the full moon, most frequently on lunar day 17, and near sunset (1,800 h). Mean fecundity (mature ova cm−2 live tissue) estimates were significantly different for two sites and ranged from ~1,780 (Saboga Island, Gulf of Panama, seasonally upwelling) to ~4,280 (Uva Is, Gulf of Chiriqui, non-upwelling). Assuming three annual spawning events colony−1 (August, September, October), extrapolation of minimum and maximum fecundities yield 5,340 and 12,840 ova cm−2 year−1. Seasonal, lunar, and diel spawning patterns in nine zooxanthellate species at Uva Island indicate asynchronous coral community spawning.

A revision of the genus Heterogorgia Verrill, 1868 (Anthozoa: Octocorallia: Plexauridae) ODALISCA BREEDY (Costa Rica) & HECTOR M. GUZMAN (Republic of Panama )

Abstract: The genus Heterogorgia Verrill, 1868 is poorly known. Lack of good illustrations and clear definitions have historically led authors to assign or transfer species erroneously to it. The genus was established by Verrill for three eastern Pacific species, another was described by Breedy and Guzman in 2005, and the geographic distribution was extended with the discovery of a western Atlantic species described by Castro in 1990. Heterogorgia is characterised by colonies composed of a number of stout stems that branch laterally and irregularly and arise from a conspicuous spreading holdfast. Coenenchymal sclerites are mostly colourless spindles; anthocodiae have strong spindles arranged in collaret and points; and the calyces are prominently armed with whorls of strongly projecting thorns. To define Heterogorgia we examined original type material of all eastern Pacific and western Atlantic species described until now and reference specimens from recent expeditions along the eastern Pacific. Morphological characters are analysed and illustrated using scanning electron micrographs. Lectotypes are designated for H. tortuosa and H. verrucosa to establish their taxonomic status. We conclude that Heterogorgia is comprised of five valid species at present: Heterogorgia hickmani and H. verrucosa for the Galapagos Islands and Ecuador mainland; H. papillosa for Mexico; H. tortuosa and H. verrucosa for Costa Rica and Panama; and H. uatumani for Brazil and Bahamas. The genera Astromuricea , Bebryce , Echinogorgia and Psammogorgia are proposed for the western Pacific species that were historically misplaced in Heterogorgia . We recommend that regional biodiversity estimates and biogeography analyses consider the erroneous status of the species that are still listed as Heterogorgia within the data sets.

A revision of the genus Heterogorgia Verrill, 1868 (Anthozoa: Octocorallia: Plexauridae)

Abstract: The genus Heterogorgia Verrill, 1868 is poorly known. Lack of good illustrations and clear definitions have historically led authors to assign or transfer species erroneously to it. The genus was established by Verrill for three eastern Pacific species, another was described by Breedy and Guzman in 2005, and the geographic distribution was extended with the discovery of a western Atlantic species described by Castro in 1990. Heterogorgia is characterised by colonies composed of a number of stout stems that branch laterally and irregularly and arise from a conspicuous spreading holdfast. Coenenchymal sclerites are mostly colourless spindles; anthocodiae have strong spindles arranged in collaret and points; and the calyces are prominently armed with whorls of strongly projecting thorns. To define Heterogorgia we examined original type material of all eastern Pacific and western Atlantic species described until now and reference specimens from recent expeditions along the eastern Pacific. Morphological characters are analysed and illustrated using scanning electron micrographs. Lectotypes are designated for H. tortuosa and H. verrucosa to establish their taxonomic status. We conclude that Heterogorgia is comprised of five valid species at present: Heterogorgia hickmani and H. verrucosa for the Galapagos Islands and Ecuador mainland; H. papillosa for Mexico; H. tortuosa and H. verrucosa for Costa Rica and Panama; and H. uatumani for Brazil and Bahamas. The genera Astromuricea, Bebryce, Echinogorgia and Psammogorgia are proposed for the western Pacific species that were historically misplaced in Heterogorgia. We recommend that regional biodiversity estimates and biogeography analyses consider the erroneous status of the species that are still listed as Heterogorgia within the data sets.

PAPER Variation in reef fish and invertebrate communities with level of protection from fishing across the Eastern Tropical

Abstract: Aim To quantify general differences in reef community structure between wellenforced and poorly enforced marine protected areas (MPAs) and fished sites across the Eastern Tropical Pacific (ETP) regional seascape Location The Pacific continental margin and oceanic islands of Costa Rica, Panama, Colombia and Ecuador, including World Heritage sites at Galapagos, Coiba, Cocos and Malpelo Methods Densities of reef fishes, mobile and sessile invertebrates, and macroalgae were quantified using underwater visual surveys at 136 ‘no-take’ and 54 openly fished sites associated with seven large MPAs that encompassed a range of management strategies. Spatial variation in multivariate and univariate community metrics was related to three levels of fishing pressure (high-protection MPAs, limited-protection MPAs, fishing zones) for both continental and oceanic reefs. Results High-protection MPAs possessed a much greater biomass of higher carnivorous fishes, lower densities of asteroids and Eucidaris spp. urchins, and higher coral cover than limited-protection MPAs and fished zones. These results were generally consistent with the hypothesis that overfishing of predatory fishes within the ETP has led to increased densities of habitat-modifying macroinvertebrates, which has contributed to regional declines in coral cover. Major differences in ecological patterns were also evident between continental and oceanic biogeographic provinces. Main conclusions Fishing down the food web, with associated trophic cascades, has occurred to a greater extent along the continental coast than off oceanic islands. Poorly enforced MPAs generate food webs more similar to those present in fished areas than in well-protected MPAs.