Scatena F.N.

Linking habitat stability to floods and droughts: effects on shrimp in montane streams, Puerto Rico

COVICH, A. P., T. A. CROWL, AND F. N. SCATENA. 2000. Linking
habitat stability to floods and droughts: effects on
shrimp in montane streams, Puerto Rico. Verhandlungen
der Internationalen Vereinigung fu¨ r theorestische und
angewandte Limnologie 27:2430–2434.

Abstract: 
Most previous studies on Caribbean flood and drought frequency have examined hydrological (e.g. MORRIS & VAZQUEZ 1990, GARCIA et al. 1996) rather than ecological effects (COVICH et al. 1998). We analyzed temporal and spatial distributions of rainfall, stream flow, and mean maximum pool depth over an 8-year period (1990–1997) to evaluate effects of variable flows. We examined the response of a biotic variable (the coefficient of variation in shrimp densities) to changes in water depth (coefficient of variation of maximum pool depth) along an elevational gradient.

Water Withdrawn From the Luquillo Experimental Forest, 2004

Crook, Kelly E.; Scatena, Fred N.; Pringle, Catherine M. 2007. Water Withdrawn From the Luquillo Experimental Forest, 2004. U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry. Gen. Tech. Rep. IITF-GTR-34.

Abstract: 
This study quantifies the amount of water withdrawn from the Luqillo Experimental Forest (LEF) in 2004. Spatially averaged mean monthly water budgets were generated for watersheds draining the LEF by combining long-term data from various government agencies with estimated extraction data. Results suggest that, on a typical day, 70 percent of water generated within the forest is diverted before reaching the ocean. This is up from an estimated 54 percent in 1994. Analysis showed that up to 63 percent of average monthly stream runoff is diverted from individual watersheds during drier months. Watersheds with large water intakes have the most dramatic decrease in streamflow, particularly the Río Espiritu Santo watershed, where 82 percent of median flow is diverted.

Linking habitat stability to floods and droughts: effects on shrimp in montane streams, Puerto Rico

Covich A.P., Crowl T.A. & Scatena F.N. (2000) Linking
habitat stability to floods and droughts: effects on
shrimp in montane streams, Puerto Rico. Verhandlungen
der Internationalen Vereinigung fu¨r Theoretische und
Angewandte Limnologie, 27, 2430–2434.

Abstract: 
Most previous studies on Caribbean flood and drought frequency have examined hydrological (e.g. MORRIS & VAZQUEZ 1990, GARCIA et al. 1996) rather than ecological effects (COVICH et al. 1998). We analyzed temporal and spatial distributions of rainfall, stream flow, and mean maximum pool depth over an 8-year period (1990–1997) to evaluate effects of variable flows. We examined the response of a biotic variable (the coefficient of variation in shrimp densities) to changes in water depth (coefficient of variation of maximum pool depth) along an elevational gradient.

FLASHINESS INDICES FOR URBAN AND RURAL STREAMS IN PUERTO RICO

Abstract: 
Urbanization and increases in impervious area are known to increase stream runoff and flashiness and several indices have been developed to quantify flashiness in temperate streams. The effectiveness of these indices in the humid tropics and how urbanization influences the flashiness of tropical streams that are known for their inherent flashiness is poorly understood and documented. This study compares two existing flashiness indices and a new approach that quantifies flashiness by the average time between large events on 13 urban to forested streams in Northeastern Puerto Rico. The average time between events of specific magnitudes, the Richards-Baker Flashiness index, and a Frequency of Stage Change approach were calculated and compared using average daily, hourly, and 15 minute discharge data. All analysis was based on USGS discharge records for the same 10 year period, 2000 through 2009. The results indicate that when flashiness is based on average daily stream flow, there was little to no discernible difference in the flashiness of the urban and forested streams. This results because average daily discharge records miss or underestimates the magnitude, duration, and the frequency of most events. When comparing the time between events of a given magnitude using hourly or 15 minute discharge series, the urban drainages have a shorter time period between peaks of a given magnitude than rural drainages. The Frequency of Stage Change approach also indicates that high density urban drainages are flashier than drainages with forested or mixed land use. For the average days and the stage frequency change method, flashiness indices based on hourly time series are similar to those based on the 15 minute series. The analysis indicates that tropical urban streams are flashier than their rural counterparts; however the difference is less than has been reported in temperate studies and is only statistically apparent when using high resolution discharge records.

THE SPATIAL ARRANGEMENT OF NERITINA VIRGINEA (GASTROPODA: NERITIDAE) DURING UPSTREAM MIGRATION IN A SPLIT-CHANNEL REACH

BLANCO,JUAN F.;SCATENA,FREDERICK N. 2007. The spatial arrangement of neritina virginea (gastropoda: neritidae) during upstream migration in a split-channel reach.. River Res. Applic. 23: 235-245.

Abstract: 
This paper relates differences in flow hydraulics between a main channel (MC) and a side channel (SC) of a river to patterns of upstream migration by Neritina virginea (Neritidae: Gastropoda), a dominant diadromous snail in streams of Puerto Rico (Greater Antilles). Near-bed water velocity, snail density and shell size were measured on a weekly basis between August and December 2000 along cross-sections in a main channel (MC) and an adjacent channel (SC) under a bridge crossing of the Rio Mameyes of Northeastern Puerto Rico. Near-bed velocity and water depth were used to compute Reynolds (Re) and Froude (Fr) numbers, and to classify flows within each channel. During base flow conditions (<2m3 s1), flow was chaotic and supercritical (Fr>1) in the MC, and non-chaotic and subcritical (Fr<1) in the SC. Higher mean densities (>100 indm2) of relatively small snails (mean s.d., 6.3 2.8 mm) were consistently recorded in the MC. Conversely, the SC had lower mean densities(<20 indm2) and significantly larger snails (7.6 2.4 mm). Within the MC, migratory groups preferred near-bed velocities>0.8ms1. Within the SC, they preferred the channel thalweg and depths>30 cm. The spatial arrangement that was observed between and within the channels may be related to food resources, predation pressure or biomechanics. Characteristics of preferred upstream migration pathways of N. virginea must be accounted when building road crossings incoastal streams with diadromous fauna.

Floods, Habitat Hydraulics and Upstream Migration of Neritina virginea (Gastropoda: Neritidae) in Northeastern Puerto Rico

BLANCO, JUAN F.; SCATENA, FREDERICK N. 2005. Floods, Habitat Hydraulics and Upstream Migration of Neritina virginea (Gastropoda: Neritidae) in Northeastern Puerto Rico.. Caribbean Journal of Science, Vol. 41, No. 1, 55-74, .

Abstract: 
Massive upstream migrations of neritid snails (Neritidae: Gastropoda) occur in tropical and subtropical streams worldwide, but their seasonality and proximate causes are unknown. We monitored massive upstream migrations of Neritina virginea for 99 weeks, and conducted a detailed study of snail density, size, and hydraulic descriptors in lower Río Mameyes, northeastern Puerto Rico. The study assessed the 1) timing and seasonality of upstream migration, 2) size composition of migratory aggregations, 3) patterns of habitat use, and 4) role of floods on upstream migration. Massive upstream migrations (500–3000ind/m2) were observed in 44 of 99 weeks of observation. While N. virginea aggregations occurred at random time intervals, they were clumped during rainy periods. Migratory aggregations consisted mostly of small individuals (5-7 mm). Greater mean density was consistently observed in a stable riffle than in an unstable run (115.7 and 17.8 ind/m2, respectively), but mean density increased and mean size reduced in both reaches during the first 7 upstream migratory events. N. virginea density and size dynamics differed between reaches as a function of habitat hydraulics. While juveniles used the stable riffle as a permanent habitat and preferred passageway, they also used an adjacent, unstable reach after storm events. Density variation was correlated with days postflood (>3.5 m3/s) in both reaches. Our observations indicated that massive upstream migrations of N. virginea juveniles occur at least once a month, presumably as habitat-dependent responses to floods.

Hierarchical contribution of river–ocean connectivity, water chemistry, hydraulics, and substrate to the distribution of diadromous snails in Puerto Rican streams

Blanco, Juan F.; Scatena, Frederick N. 2006. Hierarchical contribution of river-ocean connectivity, water chemistry, hydraulics, and substrate to the distribution of diadromous snails in Puerto Rican streams.. J. N. Am. Benthol. Soc., 25(1) :82-98.

Abstract: 
Diadromous faunas dominate most tropical coastal streams and rivers, but the factors controlling their distribution are not well understood. Our study documents abiotic variables controlling the distribution and abundance of the diadromous snail Neritina virginea (Gastropoda:Neritidae) in the Caribbean island of Puerto Rico. An intensive survey of N. virginea density and shell size, and channel substrate, velocity, and depth was conducted at microhabitat, habitat, and reach scales of a coastal plain reach of the Río Mameyes between August and December 2000. In addition, the inland extent of distribution (stream-network scale) and presence (regional scale) of N. virginea were surveyed in 32 coastal rivers around the island during summer 2001 and 2003. At the microhabitat scale, snail density and microhabitat electivity were greater in patches consisting of a mix of boulders and cobbles than in other types of substrate. At the habitat scale, snail density increased with depth. At the reach scale, snail density increased with fast and turbulent flows (riffle > pools > pond), whereas snail size showed the opposite pattern. At the regional scale, populations were present in 13 of 32 streams. Populations of N. virginea were not found in rivers that were disconnected from the ocean for most of the year because of channel dewatering, formation of sediment bars at their mouths, and low mean monthly discharge (Q=0.69 m3/s). In contrast, rivers with N. virginea populations had a permanent (Q=4.04 m3/s) or seasonal (Q=2.88 m3/s) connection to the ocean over the year. At the regional scale, the inland distribution of populations was not correlated with stream gradient, but was negatively correlated with concentrations of SiO2, P, and acid neutralizing capacity of the water. Populations colonized montane reaches in only 5 rivers, all of which were forested and protected. Our study highlights the importance of taking a hierarchical approach in managing tropical coastal rivers, and the usefulness of neritid snails as biological indicators of the physical and chemical integrity of rivers.

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.

Asynchronous fluctuation of soil microbial biomass and plant litterfall

Ruan, H.H., Zou, X.M., Scatena, F.N., Zimmerman, J.K.,
2004. Asynchronous fluctuations of soil microbial
biomass and plant litterfall in a tropical wet forest.
Plant Soil 260, 147–154.

Abstract: 
Carbon availability often controls soil microbial growth and there is evidence that at regional scales soil microbial biomass is positively correlated with aboveground forest litter input. We examined the influence of plant litterfall on annual variation of soil microbial biomass in control and litter-excluded plots in a tropical wet forest of Puerto Rico. We also measured soil moisture, soil temperature, and plant litterfall in these treatment plots. Aboveground plant litter input had no effect on soil microbial biomass or on its pattern of fluctuation. Monthly changes in soil microbial biomass were not synchronized with aboveground litter inputs, but rather preceeded litterfall by one month. Soil microbial biomass did not correlate with soil temperature, moisture, or rainfall. Our results suggest that changes in soil microbial biomass are not directly regulated by soil temperature, moisture, or aboveground litter input at local scales within a tropical wet forest, and there were asynchronous fluctuation between soil microbial biomass and plant litterfall. Potential mechanisms for this asynchronous fluctuation include soil microbial biomass regulation by competition for soil nutrients between microorganisms and plants, and regulation by below-ground carbon inputs associated with the annual solar and drying-rewetting cycles in tropical wet forests.

Litter Dynamics Along Stream, Riparian and Upslope Areas Following Hurricane Hugo, Luquillo Experimental Forest, Puerto Rico

Litter Dynamics Along Stream, Riparian and Upslope Areas Following Hurricane Hugo, Luquillo Experimental Forest, Puerto Rico
K. A. Vogt, D. J. Vogt, P. Boon, A. Covich, F. N. Scatena, H. Asbjornsen, J. L. O'Harra, J. Perez, T. g. Siccama, J. Bloomfield and J. F. Ranciato
Biotropica
Vol. 28, No. 4, Part A. Special Issue: Long Term Responses of Caribbean Ecosystems to Disturbances (Dec., 1996), pp. 458-470

Abstract: 
Litterfall (fine and coarse) due to Hurricane Hugo and subsequent fine annual litterfall inputs (1, 2 and 5 yr after Hugo) were determined for two sites (El Verde and Bisley) in the Luquillo Experimental Forest in Puerto Rico. Litter transfers into streams, riparian and upslope areas were determined within each catchment. The recovery rate of aboveground fine litterfall (leaf, fine wood <1 cm diameter, and other miscellaneous inputs) to predisturbance levels were determined 1, 2, and 5 yr after Hurricane Hugo. The amount of total litter transfers and their individual components into the riparian and upslope areas due to Hurricane Hugo varied significantly by catchments within the Luquillo Experimental Forest. At El Verde, 26-39 percent, 31-35 percent, 14-35 percent and 7-12 percent of the total litter transfers were contributed by leaf litter, fine wood, coarse wood and fine roots, respectively. At Bisley, 28-31 percent, 26-29 percent, 33-35 percent and 8-10 percent of the litter transfers were contributed by the same categories. Differential decay rates contributed to the relative importance of fine and coarse litter inputs. The recovery of fine aboveground litterfall to pre-hurricane levels after 5 yr varied by topographic location (streams had the slowest recovery, upslope areas the highest) and catchment (El Verde: 55-77%; Bisley: 39-82% of pre-hurricane values).
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