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Catherine M. Pringle	cpringle@uga.edu
Eda C. Melendez-Colom	emelend@ites.upr.edu

DATA SET IDENTIFIER:  Experimentally manipulated biota over a 30-40d period in two streams with distinctly different macrobiotic (Shrimp/Organic Matter/Ecology (1999))

PROJECT TITLE: Influence of Decapods on Ecosystem Processes

PROJECT DESCRIPTION: Three experiments were performed to study the influence of decapods on ecosystem processes. In the first one (catalogued as LTERDBAS #104) the hypothesis that differences in macrobiotic assemblages can lead to differences in the quantity and quality of organic matter in benthic depositional environmentsamong streams in montane Puerto Rico was tested. The experimental results were 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 showed 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.

In the second experiment (LTERDBAS #105) the role of freshwater shrimp, which dominate the faunal biomass of many tropical headwater streams, was studied. The enclosure/exclosure experiments in a montane Puerto Rican stream the direct and indirect effects of two dominant taxa of atyid (Atyidae) shrimp, Atya lanipes Holthius and Xiphocaris elongata Guerin-Meneville was examined. Both shrimp taxa caused significant reductions in sediment cover on rock substrata, reducing sedimentation and enhancing algal biovolume on clay tiles in cages.We evaluated the mechanism by which A. lanipes influences algae and benthic insects by comparing patterns of algal biomass, taxonomic composition and shrimp-presence treatments both with and without manual sediment removal. The shrimp exclusion treatment without manual sediment removal had significantly lower algal biomass and greater sedimentation than all other treatments. The treatment in which shrimp were excluded but sediment was manually removed, however, accrued almost the same algal biovolume as the shrimp enclosure treatment, supporting the hypothesis that sediment removal enhances the biovolume of understory algal taxa.

The effects of biotic (shrimp) and abiotic (discharge) factors on the depositional environment were quantified in a montane stream in Puerto Rico in a third experiment (LTERDBAS #106). Electricity was used experimentally to exclude large (approximately >1cm in length) biota without artificially increasing sedimentation as in cage enclosure/exclosure experiments in stream systems. Unelectrified control substrata had natural high densities of atyid shrimp. Atyid shrimp can significantly affect the accumulation of organic and inorganic materials on rock substrata in stream pools between high-discharge events.

LTER CORE AREAS: (Annotate all that apply)

Organic Matter Accumulation

LEF LTER 1 RESEARCH TOPIC: (Annotate all that apply)

System properties

We define a data file as a component of a data set. A data set can have only one data file or more. Basically, different data files have different data structures or format.
DATA SET FILES (SUBSETS):

Data File No.	Data File Identifier	On-Line Filename	Starting Date	Periodicity of sample	End Period
1	The number of shrimps and fishes observed visiting control hoops in the Sonadora (June 20, 1994 to July 30, 1994) and Bisley (July 14, 1994 to August 13, 1994) over each experimental period. Figure 2.	Fig2.txt	June 20, 1994	Once	August 13, 1994
2	Total suspended particulate material over time in Sonadora (June 20, 1994 to July 30, 1994) and Bisley (July 14, 1994 to August 13, 1994) streams throughout each experiment. Figure 3.	Fig3.txt	June 20, 1994	Once	August 13, 1994
3	Accrual of inorganic and ash-free dry mass of benthic particulate material in macrobiota exclusion and control treatments in Sonadora (June 20, 1994 to July 30, 1994) and Bisley (July 14, 1994 to August 13, 1994) streams during each experiment. Figures 4 and 5.	Fig45.txt	June 20, 1994	Once	August 13, 1994
4	Carbon and Nitrogen, associated with benthic particulate material in macrobiota exclusion and control treatments in Sonadora (June 20, 1994 to July 30, 1994) and Bisley (July 14, 1994 to August 13, 1994) streams during experimental period. Figures 6, 7, and 8.	Fig678.txt	June 20, 1994	Once	August 13, 1994

RESEARCH LOCATION: The experiments were carried our in two easily accessible streams characterized by different macrobiotic assemblages: the Sonadora (third to fourth order) and Bisley-3. The Sonadora is located in the Espiritu Santo drainage and Bisley is located in the adjacent Mameyes drainage to the east

INVESTIGATORS:

PRINCIPAL INVESTIGATORS E-MAIL address

Catherine M. Pringle

cpringle@uga.edu

OTHER RESEARCHERS E-MAIL address

Nina Hemphill
W.H. McDowell	bill.mcdowell@unh.edu
Angel Bednarek
James G. March

CONTACT PERSONS E-MAIL address Phone Number (Include area code)

Catherine M. Pringle

cpringle@uga.edu

(706) 542-1120

DATA SET 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 30-40d 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. To incorporate the natural hydrologic regime and to avoid confounding artifacts associated with cage enclosure/exclosure (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 th quantity of fine particulate organic material and associated nitrogen in benthic environments, omnivorous shrimps potentially affect the 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 cells0 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.

DATA SET METHODS: Biotic manipulations were conducted in the Sonadora and 30 d in the Bisley - 3 stream. Experiments were staggered to accomodate other studies being conducted in these gauged watersheds. In both streams we used circular electrified "fences" (hoops) to excludes fishes and shrimps larger than 1 cm in length from foraging within specific areas of the stream bottom. For a more detailed description of the methodology see publication .

REFERENCES:

CROSS REFERENCES (other data sets related to this one): LTERDBAS 104  :Shrimp/ Organic Matter/ Ecology (1999); LTERDBAS 105  :Shrimp/ Algae/ Oecologia (1993); LTERDBAS 106: Shrimp/ Algae/ Can J. Fish Aquat. Sci. (1994)

INVESTIGATOR'S ASSIGNED KEYWORDS: carbon, Decapoda, deposition, electric exclusion, fine particulate material, organic and inorganic, fishes, nitrogen, omnivorous macrobiota, Puerto Rico, seston, shrimps, tropical stream.

LEF LTER OFFICIAL KEYWORDS (See table): Q SONADORA, BISLEY WATERSHEDS Q3, RIVER, NITROGEN, SEDIMENTATION, DECAPODS, PEER REVIEWED JOURNAL

PUBLICATIONS:

Variable Name	Formula

FOR DATA MANAGER USE ONLY

DATE OF LAST REVIEW: May 2, 2008