Greathouse E.A.

Recovery of a tropical stream after a harvest-related chlorine poisoning event

GREATHOUSE, EFFIE A.; MARCH, JAMES G.; PRINGLE; CATHERINE M. 2005. Recovery of a tropical stream after a harvest-related chlorine poisoning event.. Freshwater Biology 50, :603-615.

Abstract: 
1. Harvest-related poisoning events are common in tropical streams, yet research on stream recovery has largely been limited to temperate streams and generally does not include any measures of ecosystem function, such as leaf breakdown. 2. We assessed recovery of a second-order, high-gradient stream draining the Luquillo Experimental Forest, Puerto Rico, 3 months after a chlorine-bleach poisoning event. The illegal poisoning of freshwater shrimps for harvest caused massive mortality of shrimps and dramatic changes in those ecosystem properties influenced by shrimps. We determined recovery potential using an established recovery index and assessed actual recovery by examining whether the poisoned reach returned to conditions resembling an undisturbed upstream reference reach. 3. Recovery potential was excellent (score ¼ 729 of a possible 729) and can be attributed to nearby sources of organisms for colonisation, the mobility of dominant organisms, unimpaired habitat, rapid flushing and processing of chlorine, and location within a national forest. 4. Actual recovery was substantial. Comparison of the reference reach with the formerly poisoned reach indicated: (1) complete recovery of xiphocaridid and palaemonid shrimp population abundances, shrimp size distributions, leaf breakdown rates, and abundances of oligochaetes and mayflies on leaves, and (2) only small differences in atyid shrimp abundance and community and ecosystem properties influenced by atyid shrimps(standing stocks of epilithic fine inorganic and organic matter, chlorophyll a, and abundances of chironomids and copepods on leaves). 5. There was no detectable pattern between any measured variables and distance downstream from the poisoning. However, shrimp size-distributions indicated that the observed recovery may represent a source-sink dynamic, in which the poisoned reach acts as a sink which depletes adult shrimp populations from surrounding undisturbed habitats. Thus, the rapid recovery observed in this study is consistent with results from other field studies of pulse chlorine disturbances, harvest-related fish poisonings, and recovery of freshwater biotic interactions, but it is unlikely to be sustainable if multiple poisonings deplete adult populations to the extent that juvenile recruitment does not offset adult shrimp mortality.

Do small-scale exclosure/enclosure experiments predict the eVects of large-scale extirpation of freshwater migratory fauna?

Do Small-Scale Exclosure/Enclosure Experiments Predict the Effects of Large-Scale Extirpation of Freshwater Migratory Fauna?
Effie A. Greathouse, Catherine M. Pringle and William H. McDowell
Oecologia
Vol. 149, No. 4 (Oct., 2006), pp. 709-717

Abstract: 
A variety of theoretical and empirical studies indicate that the abilities of small-scale experiments to predict responses to large-scale perturbations vary. Small-scale experiments often do not predict the directions of large-scale responses, and relatively few empirical studies have examined whether small-scale experiments predict the magnitudes of large-scale responses. Here we present an empirical example of small-scale manipulations predicting not only the directions but also the magnitudes of the eVects of whole-catchment, decades-long decimation of migratory freshwater shrimp populations. In streams of Puerto Rico (USA), we used arena sizes of < 2 m2 in 1- to 4-week exclosure/enclosure experiments. EVects of small-scale experiments largely matched those of largescale shrimp loss above dams for a variety of response variables (abiotic and biotic factors including epilithic Wne sediments, algae and organic matter, and invertebrate grazers, detritivores, and predators). The results of our extrapolation contrast with studies of small- versus large-scale perturbations in the temperate zone. Our Wndings are likely explained by: a set of response variables that are more dominated by within-patch processes than exchange processes, an experimental manipulation that encompassed the characteristic scales of response variables, our use of open arenas lacking cage artifacts, and/or our combination of two distinct experimental approaches (exclosures and enclosures). Based on our study design, we suggest that extrapolation across experimental scales can be greatly enhanced by embedding open arenas within large-scale conditions that represent all treatment levels.

Recovery of a tropical stream after a harvest-related chlorine poisoning event

GREATHOUSE, EFFIE A.; MARCH, JAMES G.; PRINGLE; CATHERINE M. 2005. Recovery of a tropical stream after a harvest-related chlorine poisoning event.. Freshwater Biology 50, :603-615.

Abstract: 
1. Harvest-related poisoning events are common in tropical streams, yet research on stream recovery has largely been limited to temperate streams and generally does not include any measures of ecosystem function, such as leaf breakdown. 2. We assessed recovery of a second-order, high-gradient stream draining the Luquillo Experimental Forest, Puerto Rico, 3 months after a chlorine-bleach poisoning event. The illegal poisoning of freshwater shrimps for harvest caused massive mortality of shrimps and dramatic changes in those ecosystem properties influenced by shrimps. We determined recovery potential using an established recovery index and assessed actual recovery by examining whether the poisoned reach returned to conditions resembling an undisturbed upstream reference reach. 3. Recovery potential was excellent (score ¼ 729 of a possible 729) and can be attributed to nearby sources of organisms for colonisation, the mobility of dominant organisms, unimpaired habitat, rapid flushing and processing of chlorine, and location within a national forest. 4. Actual recovery was substantial. Comparison of the reference reach with the formerly poisoned reach indicated: (1) complete recovery of xiphocaridid and palaemonid shrimp population abundances, shrimp size distributions, leaf breakdown rates, and abundances of oligochaetes and mayflies on leaves, and (2) only small differences in atyid shrimp abundance and community and ecosystem properties influenced by atyid shrimps(standing stocks of epilithic fine inorganic and organic matter, chlorophyll a, and abundances of chironomids and copepods on leaves). 5. There was no detectable pattern between any measured variables and distance downstream from the poisoning. However, shrimp size-distributions indicated that the observed recovery may represent a source-sink dynamic, in which the poisoned reach acts as a sink which depletes adult shrimp populations from surrounding undisturbed habitats. Thus, the rapid recovery observed in this study is consistent with results from other field studies of pulse chlorine disturbances, harvest-related fish poisonings, and recovery of freshwater biotic interactions, but it is unlikely to be sustainable if multiple poisonings deplete adult populations to the extent that juvenile recruitment does not offset adult shrimp mortality.

Does the river continuum concept apply on a tropical island? Longitudinal variation in a Puerto Rican stream

Greathouse,Effie A.; Pringle, Catherine M. 2006. Does the river continuum concept apply on a tropical island? Longitudinal variation in a Puerto Rican stream.. Can. J. Fish. Aquat. Sci. 63: 134-152.

Abstract: 
We examined whether a tropical stream in Puerto Rico matched predictions of the river continuum concept (RCC) for macroinvertebrate functional feeding groups (FFGs). Sampling sites for macroinvertebrates, basal resources, and fishes ranged from headwaters to within 2.5 km of the fourth-order estuary. In a comparison with a model temperate system in which RCC predictions generally held, we used catchment area as a measure of stream size to examine truncated RCC predictions (i.e., cut off to correspond to the largest stream size sampled in Puerto Rico). Despite dominance of generalist freshwater shrimps, which use more than one feeding mode, RCC predictions held for scrapers, shredders, and predators. Collector–filterers showed a trend opposite to that predicted by the RCC, but patterns in basal resources suggest that this is consistent with the central RCC theme: longitudinal distributions of FFGs follow longitudinal patterns in basal resources. Alternatively, the filterer pattern may be explained by fish predation affecting distributions of filter-feeding shrimp. Our results indicate that the RCC generally applies to running waters on tropical islands. However, additional theoretical and field studies across a broad array of stream types should examine whether the RCC needs to be refined to reflect the potential influence of top-down trophic controls on FFG distributions.

INDIRECT UPSTREAM EFFECTS OF DAMS: CONSEQUENCES OF MIGRATORY CONSUMER EXTIRPATION IN PUERTO RICO

GREATHOUSE, EFFIE A.; PRINGLE, CATHERINE M.; MCDOWELL, WILLIAM H.; HOLMQUIST, JEFF G. 2006. INDIRECT UPSTREAM EFFECTS OF DAMS: CONSEQUENCES OF MIGRATORY CONSUMER EXTIRPATION IN PUERTO RICO. Ecological Applications, 16(1), :339-352.

Abstract: 
Large dams degrade the integrity of a wide variety of ecosystems, yet direct downstream effects of dams have received the most attention from ecosystem managers and researchers. We investigated indirect upstream effects of dams resulting from decimation of migratory freshwater shrimp and fish populations in Puerto Rico, USA, in both high- and low-gradient streams. In high-gradient streams above large dams, native shrimps and fishes were extremely rare, whereas similar sites without large dams had high abundances of native consumers. Losses of native fauna above dams dramatically altered their basal food resources and assemblages of invertebrate competitors and prey. Compared to pools in high-gradient streams with no large dams, pool epilithon above dams had nine times more algal biomass, 20 times more fine benthic organic matter (FBOM), 65 times more fine benthic inorganic matter (FBIM), 28 times more carbon, 19 times more nitrogen, and four times more non-decapod invertebrate biomass. High-gradient riffles upstream from large dams had five times more FBIM than did undammed riffles but showed no difference in algal abundance, FBOM, or non-decapod invertebrate biomass. For epilithon of lowgradient streams, differences in basal resources between pools above large dams vs. without large dams were considerably smaller in magnitude than those observed for pools in highgradient sites. These results match previous stream experiments in which the strength of native shrimp and fish effects increased with stream gradient. Our results demonstrate that dams can indirectly affect upstream free-flowing reaches by eliminating strong top-down effects of consumers. Migratory omnivorous shrimps and fishes occur throughout the tropics, and the consequences of their declines upstream from many tropical dams are likely to be similar to those in Puerto Rico. Thus, ecological effects of migratory fauna loss upstream from dams encompass a wider variety of species interactions and biomes than the bottom-up effects (i.e., elimination of salmonid nutrient subsidies) recognized for northern temperate systems.

Conservation and management of migratory fauna and dams in tropical streams of Puerto Rico

Greathouse, E. A., C. M. Pringle, and J. G. Holmquist.
2006. Conservation and management of migratory
fauna: dams in tropical streams of Puerto
Rico. Aquatic Conservation 16:695–712.

Abstract: 
1. Compared to most other tropical regions, Puerto Rico appears to have dammed its running waters decades earlier and to a greater degree. The island has more large dams per unit area than many countries in both tropical and temperate regions (e.g., 3x that of the U.S.), and the peak rate of large dam construction occurred two and three decades prior to reported peak rates in Latin America, Asia and Africa. 2. Puerto Rico is a potential window into the future of freshwater migratory fauna in tropical regions, given the island’s extent and magnitude of dam development and the available scientific information on ecology and management of the island’s migratory fauna. 3. We review ecology, management and conservation of migratory fauna in relation to dams in Puerto Rico. Our review includes a synthesis of recent and unpublished observations on upstream effects of large dams on migratory fauna and an analysis of patterns in free crest spillway discharge across Puerto Rican reservoirs. Analyses suggest that large dams with rare spillway discharge cause near, not complete, extirpation of upstream populations of migratory fauna. They also suggest several management and conservation issues in need of further research and consideration. These include research on the costs, benefits and effectiveness of simple fish/shrimp passage designs involving simulating spillway discharge and the appropriateness of establishing predatory fishes in reservoirs of historically fishless drainages.
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