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(Data, Abstract, Methods, Variables)

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DATA SET IDENTIFIER :  Neritina snails hierarchical distribution

PROJECT DESCRIPTION :Diadromous fauna, migrating between marine and coastal streams is dominant in the neotropics. However, the factors controlling their population distribution and size are poorly understood. The migratory snail Neritina virginea (Gastropoda: Neritidae), abundant in estuaries and coastal rivers in the Caribbean, was studied to understand those factors. The objectives of the study were three-fold: 1) to identify the factors controlling the distribution of diadromous fauna at different spatial scales, 2) to determine patterns and causes of massive upstream migrations and their importance for population persistence, and 3) to integrate this knowledge into conservation strategies for migratory species and stream management plans.

After a survey of 32 coastal streams around Puerto Rico (Greater Antilles), it was evidenced that physical variables operating at different levels of the spatial hierarchy controlled longitudinal distribution of N. virginea. The hierarchically organized variables were river-ocean connectivity (regional scale), instream barriers and water chemistry (stream-network scale), habitat hydraulics (reach scale) and nearbed-flow roughness and depth (habitat scale). However, michohabitat scale distribution depended upon habitat and reach scale context. At habitat scale, water depth in pools, and nearbed flow roughness in riffles were the most important controls. At the reach scale, spatial heterogeneity among and within streambed patches was related to flow refugia, therefore controlling sensitivity of N. virginea density to flooding disturbances.

LTER CORE AREAS: Annotate all that apply (See online list)

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

RESEARCH LOCATION: Rio Mameyes at intersection with PR Route 3 (Municipality boundary between Luquillo and Rio Grande), and 32 rivers around the island directly connected to the ocean

INVESTIGATORS:

DATA SET ABSTRACT: This data set includes N. virginea densities and sizes relative to streambed substrate type, water depth, and habitat type in a low land reach in Rio Mameyes near PR Route 3 bridge, and presence and inland extent of distribution of in 32 coastal rivers around the island. Hydrologic and water chemistry variables are reported as predictors of snail distribution at regional and stream-network scales.

DATA SET METHODS: Snails were collected, counted, and measured within 0.5 x 0.5 m quadrats placed on the streambed as described in data set "Neritina snails upstream migrations":  Snails on and under rocks were counted within 0.5 x 0.5 m quadrats (n=10) placed on the streambed on a weekly basis.  Sampling quadrats were placed ˜1 m apart across the main channel (MC), and in five pairs along the side channel (SC). At SC, one quadrat of each pair was placed on the thalweg and another on the shallow part.  In addition, a random sample of individuals was collected from each quadrat to measure shell size. Shell size was measured as aperture width (straight line running along the columnella from the base of the operculum to the shell shoulder on body whorl). Total length (TL, perpendicular to AW) is related to aperture width (AW) but cannot be measured in individuals with broken outer lips (TL=1.24AW+0.04, r²=0.98).

Four habitats (point-bar and straight channel pools, a riffle, and a high flow pond) in Rio Mameyes near Route 3 Bridge were weekly sampled between August and December 2000. Water depth and substrate type were measured within each quadrat. The three-most abundant substrates were classified as boulders, cobbles, pebbles, gravel or sand/fines. Plots covered >1/3 by Elodea were classified as “mats”. Nearbed water velocity was measured along cross-sections within each habitat as described in the data set "Neritina snails upstream migrations".  In addition, the presence and inland extent of distribution of N. virginea were surveyed in 32 coastal rivers around the island during summer 2001 and 2003. Water chemistry and river discharge data were obtained from the US Geological Survey (http://nwis.waterdata.usgs.gov/usa/nwis/).

REFERENCES :

Pyron, M., and A. P. Covich. 2003. Migration patterns, densities and growth of Neritina punctulata snails in Rio Espíritu Santo and Rio Mameyes, Northeastern Puerto Rico. Caribbean Journal of Science 39:338-347.

Blanco, J. F. and F. N. Scatena. 2005. Floods, Habitat Hydraulics and Upstream Migration of Neritina virginea (Gastropoda: Neritidae) in Northeastern Puerto Rico. Caribbean Journal of Science, 41: 55-74

CROSS-REFERENCES (other data sets related to this one):  LTERDB140: Neritina snails upstream migrations

SAMPLE LOCATION :  NA

STORAGE SITES (of data files): ITES

INVESTIGATOR'S ASSIGNED KEYWORDS: freshwater gastropods, tropical streams, spatial hierarchies, landscape filters, downstream–upstream linkages

LEF LTER OFFICIAL KEYWORDS(See table):Q. Mameyes, river, discharge, population dynamics, carbon, nitrogen, phosphorus, cations, anions, other chemicals, environmental variables, human, aquatic gastropods (mollusks), dissertation, peer reviewed journal.

Blanco, J. F. 2005. Physical habitat, disturbances, and the population ecology of the migratory snail Neritina virginea (Gastropoda: Neritidae) in streams of Puerto Rico. Ph. D. Dissertation, University of Puerto Rico, Rio Piedras Campus, Department of Biology. 250 p.

Blanco, J. F. and F. N. Scatena. 2006. Hierarchical contribution of river–ocean connectivity, water chemistry, hydraulics, and substrate to the distribution of diadromous snails in Puerto Rican streams Journal of the North American Benthological Society, Vol. 25, No. 1

DISSEMINATION : UNRESTRICTED

RESTRICTED UNRESTRICTED

REASONS TO RESTRICT DATA IN THIS DATA SET BEYOND ITS TWO YEAR POLICY PERIOD*:

*WILL HAVE TO BE APPROVED BY  AT LEAST ONE LUQ LTER PRINCIPAL INVESTIGATORS: N. Brokaw, A. LUGO

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FOR DATA MANAGER USE ONLY