Canadian Journal of Fisheries and Aquatic Sciences (Impact Factor: 2.28). 06/1994; 51:1443-1450. DOI: 10.1139/f94-144

ABSTRACT Effects of biotic (shrimp) and abiotic (discharge) factors on the depositional environment were quantified in a montane stream in Puerto Rico. Electricity was used experimentally to exclude large (approximately >1 cm in length) biota without artificially increasing sedimentation as in cage enclosure/exdosure experiments in stream systems. Shrimp (>1 cm in length) were excluded from rock substrata by semicircular fences hooked up to battery-powered fence chargers which emitted continuous pulses of electricity. Unelectrified control substrata had natural high densities of atyid shrimp. Significantly greater masses of total sediment, fine and large organic particles, and algal biovolume occurred in shrimp exclusion treatments relative to controls. Shrimp exclusion treatments experienced slow and steady accumulation of sediments under base flow conditions and a large stepwise increase in sediment weight following a storm. No measurable sediment accrued in the presence of natural densities of shrimp under base flow conditions. Shrimp rapidly removed sediments that accrued during the storm (440–620 g∙m2 dry mass−1), decreasing sediment mass in control treatments to near prestorm levels (5–13 g∙m2 dry mass−1) within 30 h. Atyid shrimp can significantly affect the accumulation of organic and inorganic materials on rock substrata in stream pools between high-discharge events.

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    ABSTRACT: 2 Sharing credit as joint first authors. Contents 1. Introduction 2 2. Operational Framework 4 3. Population Biology of Guppies 7 3.1 Natural history and evolution 7 3.2 The importance of density regulation 11 4. Experimental Studies of Eco-Evo Dynamics 13 4.1 Hypotheses for eco-evo feedbacks in the evolution of LP guppies 13 4.2 Artificial streams: Retrospective studies of guppy evolution 15 4.3 Interactions between guppies and Rivulus 23 4.4 Focal streams: Prospective studies of evolution 25 5. Conclusions 34 References 36 Abstract The bulk of evolutionary ecology implicitly assumes that ecology shapes evolution, rather than vice versa, but there is increasing interest in the possibility of a two-way interaction. Dynamic feedbacks between ecological and evolutionary processes (eco-evo feedbacks) have long been recognized in the theoretical literature, and the obser-vation of rapid evolution has since inspired empiricists to explore the consequences of these feedbacks. Laboratory studies prove that short-term evolutionary change can significantly alter ecological dynamics, particularly in pair-wise interactions. We know
    Advances in Ecological Research 01/2014; 50:1-40. DOI:10.1016/B978-0-12-801374-8.00001-3 · 6.25 Impact Factor
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    ABSTRACT: Since periphytic biofilm is an important source of food in lotic ecosystems, it is important to understand how key ecological factors affect the accrual and loss of algal biomass and sediment in the biofilm. We designed a field experiment to evaluate the effects of mesohabitat type (pools and riffles), grazing fish (control and exclusion), and substrate roughness (smooth and rough) on chlorophyll a, ash-free dry mass (AFDM), and total dry mass in a subtropical stream. Mesohabitat type did not influence the effect of grazers on periphyton. However, rough substrates accumulated more total dry mass in pools than in riffles, while smooth substrates accumulated similar amounts of total dry mass in both mesohabitats. The accrual of AFDM and chlorophyll a was greater on rough than on smooth substrates, regardless of mesohabitat. Treatments without fish accrued more total dry mass, AFDM, and chlorophyll a than treatments with fish, showing that fish play a major role in this stream by removing sediment and algal biomass. These results suggest that habitat simplification in the scale of substrate roughness and loss of large grazers may impact the accrual and loss of algal biomass and sediment in lotic ecosystems.
    Hydrobiologia 07/2013; 711(1). DOI:10.1007/s10750-013-1477-x · 2.21 Impact Factor
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    ABSTRACT: Improving our understanding of the impacts of urbanization on tropical island streams is critical as urbanization becomes a dominant feature in tropical areas. Although the "urban stream syndrome" has been successful in summarizing urban impacts on streams, the response of some island streams is different to that expected. Here we review available information on urban impacts to tropical island streams and describe unique responses to urbanization. We identified three key aspects that play particularly important or unique roles in determining tropical-island stream integrity: biotic response to water pollution, movement barriers along the stream network, and altered geomorphology that results in habitat loss. As expected, water pollution negatively impacts stream ecosystems in tropical islands and in some regions impacts can be severe, as untreated wastewaters are directly discharged into streams. While aquatic insects show the expected responses to pollution, other native fauna (e.g., shrimps and fishes) appear to be less impacted by moderate levels of pollution. Movement barriers along the stream network are especially important as much of the tropical island fauna have diadromous (either amphidromous or catadromous) life histories. Most native freshwater mollusks, shrimps, and fishes inhabiting tropical islands are diadromous and depend on unimpeded connections between freshwater and marine environments to complete their life cycles. The presence of these species in urban streams is best explained by longitudinal connectivity rather than by the degree of urban impact. Finally, in streams that remain connected to marine environments, the presence of native shrimps and fishes is strongly related to the physical habitat. Fish assemblages in channelized and severely altered stream reaches are almost completely devoid of native fauna and tend to be dominated by non-native species. In contrast, relatively diverse shrimp and fish assemblages can be found in reaches that retain their physical habitat complexity, even when they are impacted by urbanization. Our Urban Ecosyst (2012) 15:315–325
    Urban Ecosystems 08/2012; 15(2):315-325. DOI:10.1007/s11252-011-0214-3 · 1.74 Impact Factor


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