Abstract An important tenet of science is establishing the reproducibility of findings. While long‐term studies may seem ill‐suited to this goal, here we provide an example of reproducible results from repeated nutrient additions to a lake. We added nitrogen and phosphorus to Peter Lake in 9 yr of a 33‐yr study. For seven of these nine additions, phytoplankton biomass, as measured by seasonal mean chlorophyll a , increased in proportion to the rate of nutrient loading. Additionally, for these seven additions, similar nutrient loading rates resulted in mean Chl a concentrations within a roughly twofold range—an outcome within expectation given uncontrolled sources of variation in a whole‐lake manipulation. However, for two of the nine nutrient additions, Chl a concentrations were well below expected concentrations. The low chlorophyll responses co‐occurred with years having the highest water color (absorbance of light at 440 nm). The number of years of nutrient additions was too limited to strongly test the influence of color at the scale of seasonal mean values. We, therefore, tested for the effect of phosphorus load and color, on Chl a using time series models of weekly data. At the weekly scale, there was a strong negative effect of color on chlorophyll concentration. Overall, the repeated nutrient additions provided a confirmation of existing models at the whole‐lake scale and demonstrated an interesting exception to these models. Including repeated manipulations as part of long‐term studies is an important way to test generalizations and to identify unexpected outcomes that raise new questions.
Welcome to the 150th annual meeting of the Ecological Society of America. I want to extend a warm welcome to the attendees here in Columbus, OH, as well as those at the satellite locations in Albuquerque, Seattle, and Atlanta, where this opening session is being simulcast. On the sesquicentennial anniversary of ESA's founding, I want to take a moment to reflect on the historical trajectory of our discipline as we look toward the questions and challenges that will shape the future. The meeting theme this year is focused on the regional and global water problems that we as a society are confronting. Many regions of the world are contending with drinking water scarcity and irrigation shortages. These problems have been exacerbated by population growth and a warmer planet that is changing the hydrologic cycle. However, water availability and access are not the only problems we face. More than 90% of the global population experiences local, periodic interruptions in water supply due to harmful algal blooms, toxins, and other pollutants. Ecologists are playing an essential role in confronting issues of water quality and quantity. Water scarcity and pollution are not limited to the aquatic domain; they are watershed-, regional-, continental-, and global-scale problems. Ecologists have been instrumental in understanding the links between the aquatic and terrestrial biospheres, and pioneers in multidisciplinary research are working to understand the mechanisms causing these problems. Capitalizing on the ecosystem services framework that was developed over 50 years ago, ecologists have been crucial in convincing policy makers that societal resilience requires conserving species, resources, and ecosystems. Ecologists have also contributed to establishing the fundamental pillars of sustainable development by influencing environmental global policy. The role of the ecologist has evolved with the environmental issues we are facing. In many ways, we as a discipline have moved away from being “problem generators” who focus on fundamental ecological questions to become “problem solvers” who work on applied issues. This decade, for the first time, more ecologists are employed by the private sector than by government or academic institutions. As industries have increasingly been forced by governments to pay for pollution and consumers are much more concerned about environmentally friendly products, it has become essential for companies to hire ecologists to both study and decrease the environmental impacts of their business practices. Tying ecological research to profits has accelerated the pace of private sector hires and raised a number of ethical challenges. At ESA, we are committed to being global leaders in ethical training of ecological scientists. As a society, it is our mission to help ensure the highest standards of ethical conduct in both privately and publically funded research by training our membership and providing expertise when ethical questions are raised. Whether employed in the private or public sector, all ecologists have become big-data scientists. Today there are more data available at a better spatial and temporal resolution than ever before. These data, from monitoring networks that are built on programs started 50–75 years ago as well as genome sequencing platforms, are made freely available in real time. Increases in technology transfer, development, and satellite technology have pushed sensor networks into the forefront of identifying and predicting ecological change. An analysis of the articles published in Ecology over the past 50 years reveals a steady increase in the number of studies utilizing only sensor-network data. Today, three-quarters of articles in Ecology are based on sensor-network data. Such networks allow us to ask large-scale ecological questions and confront local environmental challenges. One example, which we will hear about in more depth during Tuesday's plenary lecture, is the history of the toxic algae prediction and warning system developed for Lake Erie 40 years ago. Another example is the session this week in Albuquerque on recent improvements in the small mammal trap-sensor network – SMEON – and how it is being used to track wildlife disease. A byproduct of the proliferation of sensor-based research is the removal of the ecologist from the ecosystem. Approximately 25 years ago, graduate training programs in the environmental sciences began trading out field courses for computer science and data management courses. However, it is becoming abundantly clear that the knowledge that we gain from sensors and monitoring networks is only useful when we have an understanding of the context in which the measurements are taken. To that end, I am excited to announce that ESA is partnering with several universities across the United States to begin developing a graduate training curriculum that combines sensor science with place-based research. As you learn this week about the cutting-edge research on and solutions to the environmental problems facing us, take time to consider the path that led our discipline here and where we are going in the next 150 years. Thank you for your attention and enjoy the meeting! This essay was developed through extensive conversations with and feedback from A Besterman, C Buelo, KA Emery, E Eskinazi, JA Gephart, and ML Pace.
Martin A. Simonson, Michael J. Weber, Grace M. Wilkinson and Andrew R. Annear. 2023. Annual changes in water quality and sportfish community structure following commercial harvest of common carp and bigmouth buffalo. Lake Reserv Manage. XX:XXX–XXX.Commercial harvest of common carp (Cyprinus carpio; hereafter carp) and bigmouth buffalo (Ictiobus cyprinellus; hereafter buffalo) populations had little detectable effect on shallow lake ecosystems. We tested whether carp and buffalo biomass removal affects limnological variables and fish community metrics across 6 shallow, natural lakes of northwestern Iowa using mixed effects models. Annual commercial harvest of carp ranged from 0 to 71 kg/ha; annual harvest of buffalo ranged from 0 to 356 kg/ha. Biomanipulation (i.e., commercial harvest) of carp was associated with decreases in soluble phosphorus and nitrogen concentrations, but not total phosphorus or nitrogen. Buffalo harvest was unrelated to annual changes in nutrient concentrations but was associated with reductions in chlorophyll a and phycocyanin concentrations. Secchi disk transparency and total suspended solids were unrelated to carp and buffalo harvest. Carp harvest was associated with reduced biomass of large cladocerans but no other zooplankton biomass densities; buffalo harvest was unrelated to zooplankton biomass. Species richness and rake density of aquatic macrophytes were unrelated to carp and buffalo harvest. Carp and buffalo harvest was unrelated to changes in most indices of sportfish abundance, condition, and size distribution. Our results suggest harvest of carp and buffalo <71 kg/ha has little effect on abiotic and biotic ecosystem components on short time scales and highlights the challenges associated with shallow lake restoration.
Abstract Non‐seagrass sources account for ∼ 50% of the sediment organic carbon (SOC) in many seagrass beds, a fraction that may derive from external organic matter (OM) advected into the meadow and trapped by the seagrass canopy or produced in situ. If allochthonous carbon fluxes are responsible for the non‐seagrass SOC in a given seagrass bed, this fraction should decrease with distance from the meadow perimeter. Identifying the spatial origin of SOC is important for closing seagrass carbon budgets and “blue carbon” offset‐credit accounting, but studies have yet to quantify and map seagrass SOC stocks by carbon source. We measured sediment δ 13 C, δ 15 N, and δ 34 S throughout a large (6 km 2 ), restored Zostera marina (eelgrass) meadow and applied Bayesian mixing models to quantify total SOC contributions from possible autotroph sources, Z. marina , Spartina alterniflora , and benthic microalgae (BMA). Z. marina accounted for < 40% of total meadow SOC, but we did not find evidence for outwelling from the fringing S. alterniflora salt‐marsh or OM advection from bare subtidal areas. S. alterniflora SOC contributions averaged 10% at sites both inside and outside of the meadow. The BMA fraction accounted for 51% of total meadow SOC and was highest at sites furthest from the bare subtidal‐meadow edge, indicative of in situ production. 210 Pb profiles confirmed that meadow‐enhanced sedimentation facilitates the burial of in situ BMA. Deducting this contribution from total SOC would underestimate total organic carbon fixation within the meadow. Seagrass meadows can enhance BMA burial, which likely accounts for most of the non‐seagrass SOC stored in many seagrass beds.
Abstract Phytoplankton blooms often follow nutrient enrichment. Differences among lakes in light‐absorbing dissolved organic carbon (DOC) may shift bloom thresholds to higher nutrient loads and thereby increase resilience of lakes to enrichment. To explore this idea, we measured resilience to experimental enrichment of two lakes with contrasting DOC concentrations. We compared bloom thresholds in both lakes using a model of phytoplankton response to DOC and nutrients, a dynamic time series indicator of resilience, and two empirical measures of stochastic resilience, mean exit time and median survival time. For the dynamic indicator and ecosystem model the lake with higher DOC was more resilient to enrichment. However, the distributions overlapped for stochastic indicators of resilience of the two lakes. These analyses show that DOC interacts with mixing depth and zooplankton biomass to affect resilience. Strong contrasts in DOC and many observations are needed to discern effects of DOC on resilience to enrichment.
Algal blooms, the rapid proliferation of algal biomass often to nuisance or harmful levels, diminish aquatic ecosystem services. Freshwater blooms can cause substantial economic damage by interrupting water supply, limiting recreation, and reducing property values. The interaction between eutrophication and climate change has been hypothesized to drive widespread intensification of blooms in inland waters, although there is little empirical evidence that this trend is pervasive. Here, we show that bloom intensification in inland waterbodies – defined as trends in chlorophyll‐ a of increasing bloom magnitude, severity, or duration – has not been widespread for hundreds of lakes in the US. Only 10.8% of the 323 waterbodies analyzed had significant bloom intensification. Conversely, 16.4% of the waterbodies had significant decreasing trends during the same period. While it is encouraging that bloom intensification is not currently widespread, continued efforts toward aquatic ecosystem protection and restoration are imperative for maintaining ecosystem services into the future.
