March J.G.

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.

Linking Species and Ecosystems: Different Biotic Assemblages Cause Interstream Differences in Organic Matter

Linking Species and Ecosystems: Different Biotic Assemblages Cause Interstream Differences in Organic Matter
C. M. Pringle, Nina Hemphill, W. H. McDowell, Angela Bednarek and James G. March
Ecology
Vol. 80, No. 6 (Sep., 1999), pp. 1860-1872

Abstract: 
Here we test the hypothesis that differences in macrobiotic assemblages can lead to differences in the quantity and quality of organic matter in benthic depositional environments among streams in montane Puerto Rico. We experimentally manipulated biota over a 30–40 d period in two streams with distinctly different macrobiotic assemblages: one characterized by high densities of omnivorous shrimps (Decapoda: Atyidae and Xiphocarididae) and no predaceous fishes, and one characterized by low densities of shrimps and the presence of predaceous fishes. To incorporate the natural hydrologic regime and to avoid confounding artifacts associated with cage enclosures/exclosures (e.g., high sedimentation), we used electricity as a mechanism for experimental exclusion, in situ. In each stream, shrimps and/or fishes were excluded from specific areas of rock substrata in four pools using electric “fences” attached to solar-powered fence chargers. In the stream lacking predaceous fishes (Sonadora), the unelectrified control treatment was almost exclusively dominated by high densities of omnivorous shrimps that constantly ingested fine particulate material from rock surfaces. Consequently, the control had significantly lower levels of inorganic sediments, organic material, carbon, and nitrogen than the exclusion treatment, as well as less variability in these parameters. Tenfold more organic material (as ash-free dry mass, AFDM) and fivefold more nitrogen accrued in shrimp exclosures (10.6 g AFDM/m2, 0.2 g N/m2) than in controls (1.1 g AFDM/m2, 0.04 g N/m2). By reducing the quantity of fine particulate organic material and associated nitrogen in benthic environments, omnivorous shrimps potentially affect the supply of this important resource to other trophic levels. The small amount of fine particulate organic matter (FPOM) that remained in control treatments (composed of sparse algal cells) was of higher quality than that in shrimp exclosures. This is evidenced by the significantly lower carbon-to-nitrogen (C/N) ratio (an indicator of food quality, with relatively low C/N indicating higher food quality) in the control relative to the shrimp exclosure treatment. In contrast, the stream with predaceous fishes (Bisley) was characterized by very low numbers of shrimps, and macrobiota had no significant effect on benthic sediments, organic matter, C, N, and C/N. All parameters were highly variable through time, with levels and ranges in variability similar to the shrimp exclusion treatment in the Sonadora. Our experimental results are consistent with findings of an independent survey of six streams in four different drainages. Four streams that had an abundance of omnivorous shrimps, but lacked predaceous fishes, had extremely low levels of fine benthic organic and inorganic material. In contrast, two streams that had low densities of shrimps and contained predaceous fishes had significantly higher levels. Results show a strong linkage between species and ecosystem characteristics: interstream differences in the quantity and quality of fine benthic organic matter resources were determined by the nature of the macrobiotic assemblage. Furthermore, patterns in the distribution of shrimp assemblages reflected landscape patterns in the benthic depositional environment among streams.

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.

Damming Tropical Island Streams: Problems, Solutions, and Alternatives.

MARCH,JAMES G.; BENSTEAD, JONATHAN P.; PRINGLE, CATHERINE M.; SCATENA, FREDERICK N. 2003. Damming Tropical Island Streams: Problems, Solutions, and Alternatives.. November 2003 / Vol. 53 No. 11 • BioScience.

Abstract: 
The combination of human population growth, increased water usage, and limited groundwater resources often leads to extensive damming of rivers and streams on tropical islands. Ecological effects of dams on tropical islands can be dramatic, because the vast majority of native stream faunas (fishes, shrimps, and snails) migrate between freshwater and saltwater during their lives. Dams and associated water withdrawals have been shown to extirpate native faunas from upstream reaches and increase mortality of downstream-drifting larvae. A better understanding of the effects of dams and the behavior of tropical island stream faunas is providing insights into how managers can mitigate the negative effects of existing dams and develop alternatives to dam construction while still providing freshwater for human use.We review the ecological effects of dams on tropical island streams, explore means to mitigate some of these effects, describe alternatives to dam construction, and recommend research priorities.
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