Ecosystems (hosted by AFS)

Contributed Paper Session

8:00AM The Shrinking Lake Chad!: Urgent Need for Concerted Effort By Member Countries to Save It from Extinction
Prince Emeka Ndimele, Oyindamola Lois Ewenla
Lake Chad is located in the far west of Chad, bordering on north-eastern Nigeria. Lake Chad is economically important, providing water to more than 68 million people living in the four countries surrounding it (Chad, Cameroon, Niger, and Nigeria) on the edge of the Sahara. Other ecosystem services provided by the lake are: fishing, transportation, science, etc. Lake Chad is rich in flora and fauna, which are on the decline. The impact assessment report of Lake Chad Basin noted that the demand for water for irrigation has increased fourfold due to fluctuations of the basin in response to climate cycles leading to dramatic environmental changes. In 1963, the lake surface covered 25,000 Km2 but in 2017, it covers 1,350 Km2, which represents about 1,750% reduction in surface area within 54 years and annual loss in area of approximately 438 Km2. If this trend continues, Lake Chad will completely disappear in 2020!, which is next year. The disappearance of Lake Chad is attributed to a variety of factors such as overuse of water resources, climate change, poor enforcement of environmental legislation, and weak capacity for water resources management. Member states of Lake Chad basin must come together to salvage it.
8:20AM Assessing Niger-Delta Wetland Resources: A Case-Study of Mangrove Ecosystem
Olusegun Olufemi Whenu, Adebowale Kelvin Ademiluyi
The Niger Delta is located in the Atlantic coast of Southern Nigeria and is the world’s second largest delta. The mangrove swamps of Niger Delta, which is the largest delta in Africa constitute the dominant wetland ecosystem in the Niger Delta region and covers an area of about 1,900km2. Mangroves constitute important nurseries for fishes, crustaceans, sponges, algae and other invertebrates, and also acts as a sink, retaining pollutants from contaminated tidal water. The Niger Delta mangrove together with the creeks and rivers are a major source of food and livelihood for about 30 million people. Other ecosystem services provided by this unique environment are flood control, ground water re-fill, reservoir of biodiversity, climate change mitigation, etc. This wetland is potentially a good site for ecotourism and also qualifies to be a world heritage site and Ramsar site if proper steps are taken. The benefits derivable from this fragile ecosystem are under severe threat by anthropogenic stressors. These include the installation of pipelines and seismic exploration by oil companies, crude oil pollution, deforestation, etc. This paper discusses the extent of depletion and loss of mangrove ecosystem in the Niger Delta region and the value of its goods and services.
8:40AM Do Resource Subsidies from Invasive Riparian Trees Facilitate Non-Native Fish in the Upper Colorado River Basin?
Christopher Cheek, Brandon Peoples, Reuben Goforth
Species invasion can disrupt linkages between terrestrial and aquatic ecosystems by altering timing and magnitude of cross-ecosystem subsidies. Novel subsidies, or subsidies from non-native species, may disproportionately benefit invasive consumers in recipient ecosystems. Here we test the hypothesis that resource subsidies from an invasive Russian olive tree (Elaganus agustafolia) directly facilitate non-native channel catfish (Ictalurus punctatus) in the San Juan River (NM/UT, USA). Large fluxes of carbohydrate-rich olives drop into the river in late summer and autumn and are heavily consumed (up to 70% of diet seasonally) by catfish but not native fishes. Bioenergetic modeling and experimental trials suggest that olives contribute little to catfish growth and lipid accumulation but may provide metabolic energy. We conclude that olives likely contribute an energy subsidy to catfish that may be particularly important during periods of low prey availability and high metabolic demand. Consumption of RO fruit may decrease predation pressure on native fishes and alleviate competition for other food resources. Our results illustrate how riparian invasions may facilitate aquatic consumers through cross-ecosystem subsidies.
9:00AM Ecological Thresholds in Forecast Performance for Key United States West Coast Chinook Salmon Stocks
William Satterthwaite, Kelly S. Andrews, Jennifer L. Gosselin, Correigh M. Greene, Chris Harvey, Mary Hunsicker, Stuart Munsch, Michael O’Farrell, Jameal Samhouri, Kathryn Sobocinski
Preseason abundance forecasts heavily influence management of ocean salmon fisheries off the U.S. West Coast, yet little is known about how environmental variability influences forecast performance. We compared forecasts against returns for key California-Oregon ocean fishery stocks (Sacramento and Klamath Fall Chinook) and high priority stocks of prey for endangered Southern Resident Killer Whales (multiple stocks in Puget Sound, WA). We explored how well environmental indices (at multiple locations and time lags) explained variation in forecast performance, and tested for nonlinear threshold dynamics. For the California stocks, no environmental index could explain >50% of the variation in forecast performance, but spring PDO and winter NPI of return year explained >40% of the variation for the sibling-based Sacramento Fall Chinook forecast, with nonlinearity and apparent thresholds. This suggests that conditions experienced after jacks return have the most impact on sibling-based forecast performance. For Puget Sound stocks employing various forecast methods (i.e., sibling-based, production-based, environment-based, or averaged over recent years), we detected nonlinear and threshold relationships (with R2>50%) with multiple indices and time lags. These results suggest environmental influences on preseason forecasts may create biases that unwittingly render salmon fisheries management more or less conservative, and therefore warrant further study and consideration.
9:20AM Integrating Conceptual and Qualitative Models in Integrated Ecosystem Assessments – a Case Study in the Northeast United States Large Marine Ecosystem
Robert J. Gamble, Jamie Tam, Geret DePiper, PhD, Sarah K. Gaichas, Sean M. Lucey, Patricia M. Clay, Gavin Fay, Paula S. Fratantoni, Charles T. Perretti, Patricia Pinto da Silva, Vincent Saba, Laurel A. Smith, Robert Wildermuth
A marine Integrated Ecosystem Assessment (IEA) can be a complicated and even intimidating exercise as it requires expertise from many disciplines (e.g. ecology, biology, oceanography, anthropology, economics, and more). We propose that one way to begin is through conceptual and qualitative models. We used the Mental Modeler software package to explore a case study within the Northeast US LME. Mental Modeler allows for the quick creation of nodes and linkages between those nodes, and the magnitude and uncertainty associated with each were prescribed in a collaborative setting for the Georges Bank and Gulf of Maine Ecological Production Units. Additionally, subgroups with different specialties worked on submodels, then merged them through common nodes. We used Mental Modeler to test simple climate scenarios and fishing strategies by perturbing the strength of the nodes or linkages to see the effects on the system. We explored the same scenarios and strategies using the matrices generated by Mental Modeler in a qualitative network model, QPress. Our experience in this process suggests that conceptual models are useful in the beginning stages of an IEA, and qualitative models can give the useful information on trade-offs without the need to begin with more complex quantitative models.



Contributed Paper Session
Location: Reno-Sparks CC Date: September 30, 2019 Time: 8:00 am - 9:40 am