Nutrient cycling by fish supports relatively more primary production as lake productivity increases

Animals can be important in nutrient cycling in particular ecosystems, but few studies have examined how this importance varies along environmental gradients. In this study we quantified the nutrient cycling role of an abundant detritivorous fish species, the gizzard shad (Dorosoma cepedianum), in reservoir ecosystems along a gradient of ecosystem productivity. Gizzard shad feed mostly on sediment detritus and excrete sediment-derived nutrients into the water column, thereby mediating a cross-habitat translocation of nutrients to phytoplankton. We quantified nitrogen and phosphorus cycling (excretion) rates of gizzard shad, as well as nutrient demand by phytoplankton, in seven lakes over a four-year period (16 lake-years). The lakes span a gradient of watershed land use (the relative amounts of land used for agriculture vs. forest) and productivity. As the watersheds of these lakes became increasingly dominated by agricultural land, primary production rates, lake trophic state indicators (total phosphorus and chlorophyll concentrations), and nutrient flux through gizzard shad populations all increased. Nutrient cycling by gizzard shad supported a substantial proportion of primary production in these ecosystems, and this proportion increased as watershed agriculture (and ecosystem productivity) increased. In the four productive lakes with agricultural watersheds (>78% agricultural land), gizzard shad supported on average 51% of phytoplankton primary production (range 27-67%). In contrast, in the three relatively unproductive lakes in forested or mixed-land-use watersheds (>47% forest, <52% agricultural land), gizzard shad supported 18% of primary production (range 14-23%). Thus, along a gradient of forested to agricultural landscapes, both watershed nutrient inputs and nutrient translocation by gizzard shad increase, but our data indicate that the importance of nutrient translocation by gizzard shad increases more rapidly. Our results therefore support the hypothesis that watersheds and gizzard shad jointly regulate primary production in reservoir ecosystems.     

Environmental justice as a (potentially) hegemonic concept: a historical look at competing interests between the MST and indigenous people in Brazil

ABSTRACT

This article explores the need to recognise and compensate the plurality of environmental justice claims, while paying close attention to the outcomes of the most marginalised groups – cultural and ecological – in political decision-making to avoid vestiges of hegemony. The early history of the Movimiento dos Trabalhadores Rurais sem Terra (MST) serves as a case study in which environmental justice claims clash with indigenous rights claims. In recent decades, the MST has refused settling Amazonian indigenous territories, consistent with the organisation’s Via Campesina platform, which focuses on redistributing the 50% of national territory controlled privately by Brazil’s richest 4%. Yet, in the 1970s and early 1980s, Brazil’s military government pitted landless peasants and indigenous people’s struggles against each other, circumventing land reform potentially disruptive to the country’s de facto colonial fazenda land system. This tactic pressured competing groups – landless peasants and indigenous people – to fight against each other, concluding predictably: the most powerful factions ended up getting their way, conceding less in negotiations than their less-advantageously positioned, marginalised counterparts. When marginalised groups gain concessions in environmental justice struggles, often the goods comprising those concessions come at a cost to marginalised groups with even less political visibility. Hegemonic structures of power remain non-negotiable in the process of alleviating other injustices in perceived zero-sum politics. Such systemic displacement and dispersion of violence in systems built on violence suggests hegemony affects not just to other marginalised groups, but to nonhumans too.     

Ecological Conservation Through Aesthetic Landscape Planning: A Case Study of the Lower Wisconsin State Riverway

A consequence of expanding residential development into rural areas is the potential alteration of ecological communities. Certain novel land-use policies seek practical solutions by accommodating social needs for housing while conserving biodiversity. This study investigates whether regulations designed to protect the aesthetic characteristics of a river corridor simultaneously mitigate negative effects of development on avian biodiversity, despite the absence of explicit conservation objectives. Using housing data from the US Census (1990 and 2000) and the Audubon Christmas Bird Count (1987–2000), we examined changes in housing density, avian communities, and the relationship between these two variables in a location that has adopted aesthetic landscape planning, the Lower Wisconsin State Riverway. We found that overall species diversity increased in the Riverway, but remained constant in reference areas, although the relative increase in housing density in the two areas did not differ. We also found that omnivore populations decreased in the Riverway and increased in reference sites. On the whole, our study provides preliminary evidence that aesthetic landscape planning, such as employed in the Lower Wisconsin State Riverway, might constitute a politically viable approach to conserve ecological resources.     

Naturalness and Conservation in France

This article discusses the ecological and cultural criteria underlying the management practices for protected areas in France. It examines the evolution of French conservation from its roots in the 19th century, when it focused on the protection of scenic landscapes, to current times when the focus is on the protection of biodiversity. However, biodiversity is often socially defined and may not represent an ecologically sound objective for conservation. In particular, we question the current approach to protecting a specific type of biodiversity that is at the basis of traditional landscape but does not value systems that are left to develop naturally (i.e., without significant human intervention). We present several examples of current attempts in France and Europe to managing traditional ecosystems and then discuss the values that exist in systems that develop naturally. We feel the latter systems often have much to offer in terms of biodiversity as well as providing important sites for the study of dynamic ecological communities in an ever-changing world.     

Geographic and ontogenetic variation in the diet and daily ration of the bonnethead shark, <Emphasis Type="Italic">Sphyrna tiburo</Emphasis>, from the eastern Gulf of Mexico

To examine variation in diet and daily ration of the bonnethead shark, Sphyrna tiburo (Linnaeus 1758), animals were collected from three areas in the eastern Gulf of Mexico: northwest Florida (∼29°40′N, 85°13′W), Tampa Bay near Anclote Key (∼28°10′N, 82°42.5′W), and Florida Bay (∼24°50′N, 80°48′W) from March through September, 1998–2000. In each area, diet was assessed by life stage (young-of-the year, juveniles, and adults) and quantified using five indices: percent by number (%N), percent by weight (%W), frequency of occurrence (%O), index of relative importance expressed on a percent basis (%IRI), and %IRI based on diet category (%IRI_DC). Diet could not be assessed for young-of-the-year in Tampa Bay or Florida Bay owing to low sample size. Diet analysis showed an ontogenetic shift in northwest Florida. Young-of-the-year stomachs from northwest Florida (n = 68, 1 empty) contained a mix of seagrass and crustaceans while juvenile stomachs (n = 82, 0 empty) contained a mix of crabs and seagrass and adult stomachs (n = 39, 1 empty) contained almost exclusively crabs. Crabs made up the majority of both juvenile and adult diet in Tampa Bay (n = 79, 2 empty, and n = 88, 1 empty, respectively). Juvenile stomachs from Florida Bay (n = 72, 0 empty) contained seagrass and a mix of crustaceans while adult stomachs contained more shrimp and cephalopods (n = 82, 3 empty). Diets in northwest Florida and Tampa Bay were similar. The diet in Florida Bay was different from those in the other two areas, consisting of fewer crabs and more cephalopods and lobsters. Plant material was found in large quantities in all stomachs examined from all locations (>15 %IRI_DC in 6 of the 7 life stage-area combinations, >30 %IRI_DC in 4 of the 7 combinations, and 62 %IRI_DC in young-of-the-year diet in northwest Florida). Using species- and area-specific inputs, a bioenergetic model was constructed to estimate daily ration. Models were constructed under two scenarios: assuming plant material was and was not part of the diet. Overall, daily ration was significantly different by sex, life stage, and region. The bioenergetic model predicted increasing daily ration with decreasing latitude and decreasing daily ration with ontogeny regardless of the inclusion or exclusion of plant material. These results provide evidence that bonnetheads continuously exposed to warmer temperatures have elevated metabolism and require additional energy consumption to maintain growth and reproduction. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Low to moderate levels of genetic differentiation detected across the distribution of the New Zealand abalone, Haliotis iris

Two regions of the mitochondrial genome (cytochrome oxidase I and ATPase 8–ATPase 6) were used to examine the population genetic structure of New Zealand’s endemic abalone (Haliotis iris). Samples were collected from 28 locations around New Zealand between January 2005 and February 2008. At least four phylogeographic breaks were present and occurred across the Chatham rise, in the western Cook Strait region, along the southeast coast of the South Island, and at East Cape in the North Island. Gene flow across the Chatham rise is probably limited due to infrequent dispersal across large geographic distances (~850 km), while factors limiting gene flow around the North and South Islands are less clear, and understanding these may require intense temporal and spatial sampling in complex hydrographic regions. High genetic diversity and weak genetic structure may be a general feature of abalone potentially reflecting large and/or ancient populations.     

Management Relevance of Benthic Biogeography at Multiple Scales in Coastal Waters of the Northeast U.S.

Continuing pressures from human activities have harmed the health of ocean ecosystems, particularly those near the coast. Current management practices that operate on one sector at a time have not resulted in healthy oceans that can sustainably provide the ecosystem services humans want and need. Now, adoption of ecosystem-based management (EBM) and coastal and marine spatial planning (CMSP) as foundational principles for ocean management in the United States should result in a more holistic approach. Recent marine biogeographical studies and benthic habitat mapping using satellite imagery, large-scale monitoring programs, ocean observation systems, acoustic and video techniques, landscape ecology, geographic information systems, integrated databases, and ecological modeling provide information that can support EBM, make CMSP ecologically meaningful, and contribute to planning for marine biodiversity conservation. Examples from coastal waters along the northeast coast of the United States from Delaware Bay to Passamaquoddy Bay, Maine, illustrate how benthic biogeography and bottom seascape diversity information is a useful lens through which to view EBM and CMSP in nearshore waters. The focus is on benthic communities, which are widely used in monitoring programs and are sensitive to many stresses from human activities.     

Social Dimensions of Urban Flood Experience,Exposure, and Concern

With growing urban populations and climate change, urban flooding is an important global issue, even in dryland regions. Flood risk assessments are usually used to identify vulnerable locations and populations, flooding experience patterns, or levels of concern about flooding, but rarely are all of these approaches combined. Furthermore, the social dynamics of flood concerns, exposure, and experience are underexplored. We combined geographic and survey data on household‐level measures of flood experience, concern, and exposure in Utah's urbanizing Wasatch Front. We asked: (1) Are socially vulnerable groups more likely to be exposed to flood risk? (2) How common are flooding experiences among urban residents, and how are these experiences related to sociodemographic characteristics and exposure? and (3) How concerned are urban residents about flooding, and does concern vary by exposure, flood experience, and sociodemographic characteristics? Although floodplain residents were more likely to be White and have higher incomes, respondents who were of a racial/ethnic minority, were older, had less education, and were living in floodplains were more likely to report flood experiences and concern about flooding. Flood risk management approaches need to address social as well as physical sources of vulnerability to floods and recognize social sources of variation in flood experiences and concern.