Amphibians can be important consumers in both aquatic and terrestrial habitats and may represent an important energetic link between the two, particularly in the tropics, where amphibian species richness and abundance are high. In the past 20 years, amphibian populations have declined dramatically around the world; numbers have decreased catastrophically in protected upland sites throughout the neotropics, usually resulting in the disappearance of over 75% of amphibians at a given site, particularly those species that breed in streams. Most studies of amphibian declines have focused on identifying causes and documenting changes in adult abundance, rather than on their ecological consequences. Here, we review evidence for the potential ecological effects of catastrophic amphibian declines, focusing on neotropical highland streams, where impacts will likely be greatest. Evidence to date suggests that amphibian declines will have large‐scale and lasting ecosystem‐level effects, including changes in algal community structure and primary production, altered organic matter dynamics, changes in other consumers such as aquatic insects and riparian predators, and reduced energy transfers between streams and riparian habitats. Furthermore, because of habitat and functional differences between larvae and adults in most amphibians, the loss of a single species is akin to losing two species.

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Summary Information about temporal patterns of ecological responses to species losses is integral to our understanding of the ultimate effects of declining biodiversity. As part of the Tropical Amphibian Declines in Streams (TADS) project, we quantified changes in algal biomass and N cycling in algae in upland Panamanian streams following the widespread decline of larval anurans. Reach‐scale monitoring during and after a catastrophic, disease‐driven amphibian decline showed significant 2.8‐fold increases (P < 0.05) in algal biomass in pools and 6.3‐fold increases in riffles in the 5 months following the decline. 3 years after the decline, the magnitude of this initial change dampened to increases (P < 0.05) of 2‐fold in pools and 3.5‐fold in riffles over pre‐decline levels. Similarly, total organic matter of benthic biofilms, measured as ash‐free dry mass (AFDM), increased significantly by 2.2‐fold in pools and 2.3‐fold in riffles in the initial 5‐month post‐decline period, with the magnitude of these changes dampening slightly to a 2‐fold increase in pools and 1.9‐fold increase in riffles over pre‐decline levels after 3 years (P < 0.05 for differences at 5 months and 3 years). There were initial increases (P < 0.05) in Chl a:AFDM ratios 5 months after the decline, but ratios had returned to pre‐decline levels after 3 years. Algal food quality (as C/N) increased slightly, but not significantly, during the initial 5‐month post‐decline period and remained constant over 3 years. Mean δ15N in biofilms in pool habitat (measured over the reach scale) was significantly depleted initially following tadpole declines and remained significantly depleted 3 years after the decline (4.34 ‰ pre‐ versus 3.24‰ post‐; P < 0.05), suggesting that the loss of tadpoles reduced N recycling. Increases in abundance and production of some grazing macroinvertebrate taxa after the decline may have contributed to the gradual reduction in the difference between initial and longer‐term post‐decline algal biomass. However, algal biomass was still 2‐fold greater than pre‐decline levels after 3 years, indicating that grazing macroinvertebrates did not fully compensate for the loss of tadpoles.

Benthic macroinvertebrate fauna plays a major role in river ecosystems, especially those of tropical islands. Since there is no information on the distribution of benthic invertebrates along a Jamaican river, we report here on the composition of the benthic fauna of the Buff Bay river, on the Northern coast of Jamaica. A total of 14 samples were collected from five sites, using kick nets and a Surber sampler, between May 1997 and October 1998. We also examined the applicability of the rhithron/potamon model, and some of the premises of the River Continuum Concept (RCC) in relation to the distribution of invertebrate taxa. The results showed a total of 38 taxa of identified invertebrates. A group of dominant taxa, composed mainly of immature stages of insects, occurred at all sites. Two notable characteristics of the river were the absence of a true potamonic fauna and the low representation of the shredder functional feeding group in the community We conclude that, while there was minor variation in the composition of the benthic macroinvertebrate fauna among the sites, this was a response to local conditions within the river system. The characteristics of the community did not conform to either of the models. Rev. Biol. Trop. 60 (1): 291-303. Epub 2012 March 01.

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