Freshwater Shrimp Effects on Detrital Processing and Nutrients in a Tropical Headwater Stream

Abstract

In this paper, we report on a whole-pool manipulation of leaf litter decomposition in a tropical stream following a hurricane. The study was designed to distinguish how decapod species comprising two functional feeding guilds alter rates and magnitudes of leaf litter processing and nutrient release linking the detrital food web with the overall producer-consumer food web. Streams of the Luquillo Experimental Forest, Puerto Rico, are dominated numerically by two freshwater shrimp species (Atya lanipes and Xiphocaris elongata). To determine how these shrimp affected detrital processing following large leaf inputs associated with a hurricane, we manipulated the presence or absence of two species of shrimp in six fenced pools of a headwater stream with hurricane levels of Cecropia leaf litter over a 23-d period. The experiment was designed to determine how the two different shrimp affected: (1) the rate and amount of size fractionation of leaf material; (2) the localized nutrient concentrations in the pools; and (3) the rate of particulate export from the pools. Both shrimp species influenced detrital processing, but in fundamentally different ways. Xiphocaris shred intact, large leaves and converted them into fine, medium, and coarse particulates. Through this conversion process Xiphocaris increased the concentration and rate of downstream transport of suspended particulate organic matter. Xiphocaris also significantly increased the concentration of both total dissolved nitrogen and dissolved organic carbon, likely by changing the surface area to volume ratio of organic particles. Atya, a scraper/filter feeder, caused a slight increase in rates of leaf breakdown as compared to controls at the end of the experiment but filtered out fine organic particulates, resulting in less downstream export. Both decapod species affected detrital processing, but in fundamentally different ways, illustrating the potential importance guild diversity may have in altering both particulate and nutrient availability to the rest of the food web. In addition, these results suggest that the presence of both feeding guilds can significantly influence ecosystem responses to severe, large-scale disturbance events.

Land use effects on leaf litter breakdown in low-order streams draining a rapidly developing tropical watershed in Puerto Rico

“…However, high microbial activity on leaves allows for non-shredding organisms (e.g., scraping mayflies, shrimps, snails) to consume leaf material, accelerating the process of decomposition (Bobeldyk & Ramírez, 2007;Rosemond et al, 2001) and making this energy available to higher trophic levels (Ramírez & Pringle, 2006). In addition, non-insect organisms such as decapods and fishes can consume large amounts of leaf material in tropical streams (Crowl et al, 2001;Rosemond et al, 2001).…”

“…Biotic controls on leaf breakdown in Puerto Rican streams have been mainly associated with the presence of shrimp assemblages that are able to consume leaf material (Crowl et al, 2001;March et al, 2001;Wright & Covich, 2006). However, our study watershed lack the abundant shrimp assemblages natural of many streams in Puerto Rico, due to the presence of a large dam located downstream of all our study streams (Kwak et al, 2007).…”

“…In temperate streams, insect shredders (e.g., tipulid dipterans, stoneflies) consume and convert leaf material into fine particles that are transported downstream, or consumed by other organisms (Hieber & Gessner, 2002). In warm-water tropical streams, microbial activity potentially plays a larger role in making leaf material a palatable resource not only to shredders, but also to omnivorous consumers, in particular insect collectors, omnivorous decapods (e.g., crabs and shrimps), and fishes (Crowl, McDowell, Covich & Johnson, 2001;Encalada, Calles, Ferreira, Canhoto & Graça, 2010;March, Benstead, Pringle & Scatena, 2001;Rosemond, Pringle, Ramírez & Paul, 2001;Bobeldyk & Ramírez, 2007). Therefore, in both tropical and temperate streams a great number of aquatic organisms can be potentially connected to leaf detritus entering streams (Wallace et al, 1997;Benstead et al, 2003).…”

Functional feeding groups of aquatic insect families in Latin America: a critical analysis and review of existing literature

“…Individuals inhabiting slow water areas are collectors as they remove particles from the stream bottom. However, individuals inhabiting fast flowing riffles can use the same structures to filter feeding (Crowl, McDowell, Covich & Johnson, 2001). Thus, one could assign this species to two possible FFGs depending on the habitat used and the behavior displayed by individuals.…”

Gorgona, Baudó y Darién (Chocó Biogeográfico, Colombia): ecorregiones modelo para los estudios ecológicos de comunidades de quebradas costeras

“…De hecho, se ha establecido que los camarones son los principales responsables del fraccionamiento de la hojarasca en quebradas insulares del Caribe (Pringle, Hemphill, McDowell, Bednarek & March, 1999;Crowl, McDowell, Covich & Johnson, 2001) y por lo tanto su papel en el Chocó Biogeográfico podría ser similar. Adicionalmente, Longo-Sánchez & Blanco (2014b en este número) encontraron que las cucarachas (Blaberidae: Epilampra) y otros insectos, además de los camarones Potimirin glabra, son los detritívoros dominantes en las quebradas del PNNG, lo cual pone al Chocó Biogeográfico dentro de la discusión global de la importancia de los detritívoros en el proceso de descomposición.…”