Transboundary threats in the Mekong basin: protecting a crucial fishery

This repository item contains a single issue of Issues in Brief, a series of policy briefs that began publishing in 2008 by the Boston University Frederick S. Pardee Center for the Study of the Longer-Range Future.In this Issues in Brief, Pardee Center Visiting Research Fellow Irit Altman looks at the impacts that dams in the upper Mekong River basin have on the critically important fishery in Cambodia’s Tonle Sap, the largest freshwater lake in Southeast Asia. Altman explores how development of dams, in combination with a failure of regional governance, has threatened the ecological sustainability of the lake and its watershed, and the livelihoods of people in the region. She identifies strategies to enhance the resilience of the Tonle Sap fishery and improve the lives of people who are connected to this unique ecosystem. Irit Altman is a Pardee Center Visiting Research Fellow and Research Assistant Professor of Biology at Boston University. A marine and freshwater ecologist, she works with an interdisciplinary research team to develop ecosystem models that integrate scientific knowledge and inform decision-making. She has extensive experience working with field experts and decision makers in Cambodia to understand system change and explore sustainability options in the Tonle Sap ecosystem

Trematode parasites of the mudsnail Ilyanassa obsoleta: An analysis of parasite communities at different scales

This research examines the ecological factors that shape trematode parasite communities of mudsnail Ilyanassa obsoleta at three different spatial scales. Nine species of trematode which obligately infect I. obsoleta during larval stages but use numerous estuarine species as second intermediate and definitive hosts are considered. The work provides the most geographically extensive examination to date of this trematode parasite community. At the broadest scale, I. obsoleta trematodes were examined across their distributional range (Chapter 2) which includes both native and introduced populations. The results demonstrate that introduced trematode communities are characterized by lower abundance and diversity compared to native communities and therefore conform to the pattern predicted by the enemy release hypothesis. The ecological factors that contribute to the establishment of specific L. obsoleta trematodes in the introduced range are considered. A regional scale analysis of I. obsoleta trematode communities is presented in Chapter 3. Trematode abundance and diversity along with a wide variety of biological, chemical, and physical factors was examined at fifteen salt marsh sites located throughout northern New England, USA. Although the abundance of numerous hosts were measured as part of this work, variables found to be most strongly correlated with trematode abundance and diversity at sites (revealed through multiple regression analysis) were of physical and chemical origin including sediment nitrogen, roads, trace metals and the distance of sites from the ocean. The results are explored in the context of a variety of candidate mechanisms. Chapter 4 focuses on I. obsoleta trematodes at a local scale within a single salt marsh site. The work examines intra- and inter-annual patterns of trematode infection in snails associated with four distinct salt marsh habitat types. Experiments were conducted to assess the importance of key processes in determining infection patterns including acquisition of infection by I. obsoleta, mortality, movement, and demographics of the snail hosts. Results indicate that patterns of infection among the salt marsh habitats are subject to strong shifts over time. Changing demographics and snail movement (but not infection input) are likely to be the strongest factors contributing to changing infection patterns across habitats in this system

Parasites Alter Community Structure

Parasites often play an important role in modifying the physiology and behavior of their hosts and may, consequently, mediate the influence hosts have on other components of an ecological community. Along the northern Atlantic coast of North America, the dominant herbivorous snail Littorina littorea structures rocky intertidal communities through strong grazing pressure and is frequently parasitized by the digenean trematode Cryptocotyle lingua. We hypothesized that the effects of parasitism on host physiology would induce behavioral changes in L. littorea, which in turn would modulate L. littorea\u27s influence on intertidal community composition. Specifically, we hypothesized that C. lingua infection would alter the grazing rate of L. littorea and, consequently, macroalgal communities would develop differently in the presence of infected versus uninfected snails. Our results show that uninfected snails consumed 40% more ephemeral macroalgal biomass than infected snails in the laboratory, probably because the digestive system of infected snails is compromised by C. lingua infection. In the field, this weaker grazing by infected snails resulted in significantly greater expansion of ephemeral macroalgal cover relative to grazing by uninfected snails. By decreasing the per-capita grazing rate of the dominant herbivore, C. lingua indirectly affects the composition of the macroalgal community and may in turn affect other species that depend on macroalgae for resources or habitat structure. In light of the abundance of parasites across systems, we suggest that, through trait-mediated indirect effects, parasites may be a common determinant of structure in ecological communities

Stranded capital: environmental stewardship is part of the economy, too

The many values that humans place on biodiversity are widely acknowledged but difficult to measure in practice. We address this problem by quantifying the contribution of marine-related environmental stewardship, in the form of donations and volunteer hours, to the economy of coastal Massachusetts. Our conservative evaluation suggests that marine stewardship activities contributed at least $179 million to the state economy in 2014, a figure that exceeded revenues derived in that same year from commercial finfish operations ($105 million) and whale watching ($111 million), two acknowledged cornerstones of the regional economy. Almost imperceptibly, the coastal economy has been transformed from one dependent on commercial exchange to a diverse economy that includes, to a large measure, marine stewardship. Donations and volunteer efforts are useful indicators of environmental values that can be hard to quantify, and represent one measure of human determination to protect the planet

Founder effects and species introductions: A host versus parasite perspective

Species colonizations (both natural and anthropogenic) can be associated with genetic founder effects, where founding populations demonstrate significant genetic bottlenecks compared to native populations. Yet, many successfully established free�living species exhibit little reduction in genetic diversity—possibly due to multiple founding events and/or high propagule pressure during introductions. Less clear, however, is whether parasites may show differential signatures to their free�living hosts. Parasites with indirect life cycles may particularly be more prone to founder effects (i.e., more genetically depauperate) because of inherently smaller founding populations and complex life cycles. We investigated this question in native (east coast) and introduced (west coast) North American populations of a host snail Tritia obsoleta (formerly Ilyanassa obsoleta, the eastern mudsnail) and four trematode parasite species that obligately infect it. We examined genetic diversity, gene flow, and population structure using two molecular markers (mitochondrial and nuclear) for the host and the parasites. In the host snail, we found little to no evidence of genetic founder effects, while the trematode parasites showed significantly lower genetic diversity in the introduced versus native ranges. Moreover, the parasite's final host influenced infection prevalence and genetic diversity: Trematode species that utilized fish as final hosts demonstrated lower parasite diversity and heightened founder effects in the introduced range than those trematodes using birds as final hosts. In addition, inter�regional gene flow was strongest for comparisons that included the putative historical source region (mid�Atlantic populations of the US east coast). Overall, our results broaden understanding of the role that colonization events (including recent anthropogenic introductions) have on genetic diversity in non�native organisms by also evaluating less studied groups like parasites

The role of sand lances (Ammodytes sp.) in the Northwest Atlantic ecosystem: a synthesis of current knowledge with implications for conservation and management

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Staudinger, M. D., Goyert, H., Suca, J. J., Coleman, K., Welch, L., Llopiz, J. K., Wiley, D., Altman, I., Applegate, A., Auster, P., Baumann, H., Beaty, J., Boelke, D., Kaufman, L., Loring, P., Moxley, J., Paton, S., Powers, K., Richardson, D., Robbins, J., Runge, J., Smith, B., Spiegel, C., & Steinmetz, H. The role of sand lances (Ammodytes sp.) in the Northwest Atlantic ecosystem: a synthesis of current knowledge with implications for conservation and management. Fish and Fisheries, 00, (2020): 1-34, doi:10.1111/faf.12445.The American sand lance (Ammodytes americanus, Ammodytidae) and the Northern sand lance (A. dubius, Ammodytidae) are small forage fishes that play an important functional role in the Northwest Atlantic Ocean (NWA). The NWA is a highly dynamic ecosystem currently facing increased risks from climate change, fishing and energy development. We need a better understanding of the biology, population dynamics and ecosystem role of Ammodytes to inform relevant management, climate adaptation and conservation efforts. To meet this need, we synthesized available data on the (a) life history, behaviour and distribution; (b) trophic ecology; (c) threats and vulnerabilities; and (d) ecosystem services role of Ammodytes in the NWA. Overall, 72 regional predators including 45 species of fishes, two squids, 16 seabirds and nine marine mammals were found to consume Ammodytes. Priority research needs identified during this effort include basic information on the patterns and drivers in abundance and distribution of Ammodytes, improved assessments of reproductive biology schedules and investigations of regional sensitivity and resilience to climate change, fishing and habitat disturbance. Food web studies are also needed to evaluate trophic linkages and to assess the consequences of inconsistent zooplankton prey and predator fields on energy flow within the NWA ecosystem. Synthesis results represent the first comprehensive assessment of Ammodytes in the NWA and are intended to inform new research and support regional ecosystem‐based management approaches.This manuscript is the result of follow‐up work stemming from a working group formed at a two‐day multidisciplinary and international workshop held at the Parker River National Wildlife Refuge, Massachusetts in May 2017, which convened 55 experts scientists, natural resource managers and conservation practitioners from 15 state, federal, academic and non‐governmental organizations with interest and expertise in Ammodytes ecology. Support for this effort was provided by USFWS, NOAA Stellwagen Bank National Marine Sanctuary, U.S. Department of the Interior, U.S. Geological Survey, Northeast Climate Adaptation Science Center (Award # G16AC00237), an NSF Graduate Research Fellowship to J.J.S., a CINAR Fellow Award to J.K.L. under Cooperative Agreement NA14OAR4320158, NSF award OCE‐1325451 to J.K.L., NSF award OCE‐1459087 to J.A.R, a Regional Sea Grant award to H.B. (RNE16‐CTHCE‐l), a National Marine Sanctuary Foundation award to P.J.A. (18‐08‐B‐196) and grants from the Mudge Foundation. The contents of this paper are the responsibility of the authors and do not necessarily represent the views of the National Oceanographic and Atmospheric Administration, U.S. Fish and Wildlife Service, New England Fishery Management Council and Mid‐Atlantic Fishery Management Council. This manuscript is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints for Governmental purposes. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government

Appendix D. Cross correlations among biological, chemical, and physical variables that are potential determinants of trematode prevalence and abundance.

Cross correlations among biological, chemical, and physical variables that are potential determinants of trematode prevalence and abundance

Appendix C. Analysis and discussion of relationships between prevalence of Ilyanassa obsoleta trematodes that mature in fish hosts and abundance of definitive fish hosts measured from salt marsh sites.

Analysis and discussion of relationships between prevalence of Ilyanassa obsoleta trematodes that mature in fish hosts and abundance of definitive fish hosts measured from salt marsh sites

Appendix B. Full description of methods to reduce metal data prior to analytical modeling of trematode prevalence and diversity and comparisons of metal concentrations at sites to the informal toxicity benchmark: Effect Range Low.

Full description of methods to reduce metal data prior to analytical modeling of trematode prevalence and diversity and comparisons of metal concentrations at sites to the informal toxicity benchmark: Effect Range Low

Founder effects and species introductions: A host versus parasite perspective

Species colonizations (both natural and anthropogenic) can be associated with geneticfounder effects, where founding populations demonstrate significant genetic bottlenecks compared to native populations. Yet, many successfully established free-livingspecies exhibit little reduction in genetic diversity-”possibly due to multiple founding events and/or high propagule pressure during introductions. Less clear, however, is whether parasites may show differential signatures to their free-living hosts.Parasites with indirect life cycles may particularly be more prone to founder effects(i.e., more genetically depauperate) because of inherently smaller founding populations and complex life cycles. We investigated this question in native (east coast) andintroduced (west coast) North American populations of a host snail Tritia obsoleta(formerly Ilyanassa obsoleta, the eastern mudsnail) and four trematode parasite species that obligately infect it. We examined genetic diversity, gene flow, and population structure using two molecular markers (mitochondrial and nuclear) for the hostand the parasites. In the host snail, we found little to no evidence of genetic foundereffects, while the trematode parasites showed significantly lower genetic diversityin the introduced versus native ranges. Moreover, the parasite's final host influencedinfection prevalence and genetic diversity: Trematode species that utilized fish asfinal hosts demonstrated lower parasite diversity and heightened founder effects inthe introduced range than those trematodes using birds as final hosts. In addition,inter-regional gene flow was strongest for comparisons that included the putativehistorical source region (mid-Atlantic populations of the US east coast). Overall, ourresults broaden understanding of the role that colonization events (including recentanthropogenic introductions) have on genetic diversity in non-native organisms byalso evaluating less studied groups like parasites