The ghost of the past anthropogenic impact: Reef-decapods as bioindicators of threatened marine ecosystems

Abstract

This study demonstrated the plasticity of reef-decapod according with the exposed anthropogenic pressure. Comparing the reef-decapods at sites with different anthropogenic pressures in two different ecoregions (tropical and subtropical reef ecotypes), we demonstrated that historical anthropogenic activity is molding directly and indirectly their population. A direct impact over target decapods for fishing (e.g. Lobsters and large crabs) that are removed directly by human activities. A positive indirect impact related to a top-down trophic imbalance with the increase of naturally dominant preys (small decapod) due to the removal of top predators. Thus, insufficient predators to control the abundant prey in a classic unbalanced prey-predator relationship. An indirect and negative impact, related to a bottom-up trophic imbalance, is the exclusion of niche-restricted species in association with benthic cover (e.g. corals). This also has the positive outcome, however, of increasing numbers of herbivores, detritivores and scavengers. As hypothesis, we propose that a current biodiversity balance in anthropogenically impacted ecosystem is just reflecting past trophic cascade events. Where the remaining biodiversity is monopolizing the vacant niches after the removal of components in a trophic chain. Therefore, we are suggesting that reef-decapod biodiversity, observed using visual identification, can be used to highlight the “Ghost of the past anthropogenic impact” in threatened ecosystems.

Keywords

• Taxonomy
• Marine biology
• Marine ecology
• Trophic chain
• Marine protected areas
• Anthropogenic impacts