Interactions Among Environmental Drivers: Community Responses to Changing Nutrients and Dissolved Organic Carbon

Biological communities are frequently exposed to environmental changes that cause measurable responses in properties of the community (hereafter called environmental drivers). Predicting how communities respond to changing environmental drivers is a fundamental goal of ecology. Making predictions, however, can be very difficult, particularly when multiple environmental drivers change simultaneously and there are interactions among the drivers. We investigated the effects of the interaction between changes in nutrient loading and changes in colored dissolved organic matter (measured as dissolved organic carbon, DOC) on the dynamics of phytoplankton communities over a 7‐yr period. In 1991, Long Lake, a small seepage lake in northern Michigan, was divided vertically, from sediment surface to water surface, with plastic curtains as part of a whole‐lake experiment. The accompanying changes in hydrology led to increases in DOC concentration in one of the basins. Nutrients were added to both basins from 1993 to 1997, causing dramatic changes in phytoplankton community composition. We used multivariate autoregressive models to help interpret the patterns of phytoplankton community composition observed during the experiment. DOC and nutrient addition had diverse effects on phytoplankton: some taxonomic and morphological groups were directly affected by the changes in DOC and nutrients, whereas other groups experienced indirect effects via their interactions with groups that were directly affected. Model results suggest that there was an interaction between the effects of DOC and nutrients for many groups of phytoplankton, such that differences in DOC concentration accounted for differences between basins in response to nutrient addition. The effects of DOC can be explained by changes in physical structure (e.g., thermocline depth and transparency) and water chemistry (e.g., pH) that accompanied changes in DOC concentration. The interaction between DOC and nutrients suggests that predicting community responses to multiple drivers cannot be achieved by simply adding up the effects of single drivers

Interactions among environmental drivers: Community responses to changing nutrients and dissolved organic carbon

Biological communities are frequently exposed to environmental changes that cause measurable responses in properties of the community (hereafter called environmental drivers). Predicting how communities respond to changing environmental drivers is a fundamental goal of ecology. Making predictions, however, can be very difficult, particularly when multiple environmental drivers change simultaneously and there are interactions among the drivers. We investigated the effects of the interaction between changes in nutrient loading and changes in colored dissolved organic matter (measured as dissolved organic carbon, DOC) on the dynamics of phytoplankton communities over a 7-yr period. In 1991, Long Lake, a small seepage lake in northern Michigan, was divided vertically, from sediment surface to water surface, with plastic curtains as part of a whole-lake experiment. The accompanying changes in hydrology led to increases in DOC concentration in one of the basins. Nutrients were added to both basins from 1993 to 1997, causing dramatic changes in phytoplankton community composition. We used multivariate autoregressive models to help interpret the patterns of phytoplankton community composition observed during the experiment. DOC and nutrient addition had diverse effects on phytoplankton: some taxonomic and morphological groups were directly affected by the changes in DOC and nutrients, whereas other groups experienced indirect effects via their interactions with groups that were directly affected. Model results suggest that there was an interaction between the effects of DOC and nutrients for many groups of phytoplankton, such that differences in DOC concentration accounted for differences between basins in response to nutrient addition. The effects of DOC can be explained by changes in physical structure (e.g., thermocline depth and transparency) and water chemistry (e.g., pH) that accompanied changes in DOC concentration. The interaction between DOC and nutrients suggests that predicting community responses to multiple drivers cannot be achieved by simply adding up the effects of single drivers

Ecological history affects zooplankton community responses to acidification

The effects of ecological history are frequently ignored in attempts to predict community responses to environmental change. In this study, we explored the possibility that ecological history can cause differences in community responses to perturbation using parallel acidification experiments in three sites with different pH histories in the Northern Highland Lake District of Wisconsin, USA. In Trout Lake, high acid neutralizing capacity had historically buffered changes in pH. In contrast, the two basins of Little Rock Lake (Little Rock-Reference and Little Rock-Treatment) had experienced seasonal fluctuations in pH. Furthermore, the two lake basins were separated with a curtain and Little Rock-Treatment was experimentally acidified in the late 1980s. In each site, we conducted mesocosm experiments to compare zooplankton community dynamics in control (ambient pH) and acidified (pH 4.7) treatments. Zooplankton community responses were strongest in Trout Lake and weakest in Little Rock-Treatment suggesting that ecological history affected responses to acidification. In part, variation in community sensitivity to acidification was driven by differences in species composition. However, the results of a reciprocal transplant experiment indicated that changes in the acid tolerance of populations during past acidification events may make zooplankton communities less sensitive to subsequent pH stress. Our study highlights the role that ecological history may play in community-level responses to environmental change

Trajectories Of Zooplankton Recovery In The Little Rock Lake Whole‐Lake Acidification Experiment

Understanding the factors that affect biological recovery from environmental stressors such as acidification is an important challenge in ecology. Here we report on zooplankton community recovery following the experimental acidification of Little Rock Lake, Wisconsin, USA. One decade following cessation of acid additions to the northern basin of Little Rock Lake (LRL), recovery of the zooplankton community was complete. Approximately 40% of zooplankton species in the lake exhibited a recovery lag in which biological recovery to reference basin levels was delayed by 1–6 yr after pH recovered to the level at which the species originally responded. Delays in recovery such as those we observed in LRL may be attributable to “biological resistance” wherein establishment of viable populations of key acid-sensitive species following water quality improvements is prevented by other components of the community that thrived during acidification. Indeed, we observed that the recovery of species that thrived during acidification tended to precede recovery of species that declined during acidification. In addition, correspondence analysis indicated that the zooplankton community followed different pathways during acidification and recovery, suggesting that there is substantial hysteresis in zooplankton recovery from acidification. By providing an example of a relatively rapid recovery from short-term acidification, zooplankton community recovery from experimental acidification in LRL generally reinforces the positive outlook for recovery reported for other acidified lakes

A Practical Guide for Managing Interdisciplinary Teams: Lessons Learned from Coupled Natural and Human Systems Research

Interdisciplinary team science is essential to address complex socio-environmental questions, but it also presents unique challenges. The scientific literature identifies best practices for high-level processes in team science, e.g., leadership and team building, but provides less guidance about practical, day-to-day strategies to support teamwork, e.g., translating jargon across disciplines, sharing and transforming data, and coordinating diverse and geographically distributed researchers. This article offers a case study of an interdisciplinary socio-environmental research project to derive insight to support team science implementation. We evaluate the project’s inner workings using a framework derived from the growing body of literature for team science best practices, and derive insights into how best to apply team science principles to interdisciplinary research. We find that two of the most useful areas for proactive planning and coordinated leadership are data management and co-authorship. By providing guidance for project implementation focused on these areas, we contribute a pragmatic, detail-oriented perspective on team science in an effort to support similar projects

Wind and trophic status explain within and among-lake variability of algal biomass: Variability of phytoplankton biomass

Phytoplankton biomass and production regulates key aspects of freshwater ecosystems yet its variability and subsequent predictability is poorly understood. We estimated within‐lake variation in biomass using high‐frequency chlorophyll fluorescence data from 18 globally distributed lakes. We tested how variation in fluorescence at monthly, daily, and hourly scales was related to high‐frequency variability of wind, water temperature, and radiation within lakes as well as productivity and physical attributes among lakes. Within lakes, monthly variation dominated, but combined daily and hourly variation were equivalent to that expressed monthly. Among lakes, biomass variability increased with trophic status while, within‐lake biomass variation increased with increasing variability in wind speed. Our results highlight the benefits of high‐frequency chlorophyll monitoring and suggest that predicted changes associated with climate, as well as ongoing cultural eutrophication, are likely to substantially increase the temporal variability of algal biomass and thus the predictability of the services it provides.Additional co-authors: E de Eyto, H Feuchtmayr, M Honti, V Istvánovics, C G McBride, S R Schmidt, D Seekell, P A Staehr, G Zh

Typha (Cattail) Invasion in North American Wetlands: Biology, Regional Problems, Impacts, Ecosystem Services, and Management

Typha is an iconic wetland plant found worldwide. Hybridization and anthropogenic disturbances have resulted in large increases in Typha abundance in wetland ecosystems throughout North America at a cost to native floral and faunal biodiversity. As demonstrated by three regional case studies, Typha is capable of rapidly colonizing habitats and forming monodominant vegetation stands due to traits such as robust size, rapid growth rate, and rhizomatic expansion. Increased nutrient inputs into wetlands and altered hydrologic regimes are among the principal anthropogenic drivers of Typha invasion. Typha is associated with a wide range of negative ecological impacts to wetland and agricultural systems, but also is linked with a variety of ecosystem services such as bioremediation and provisioning of biomass, as well as an assortment of traditional cultural uses. Numerous physical, chemical, and hydrologic control methods are used to manage invasive Typha, but results are inconsistent and multiple methods and repeated treatments often are required. While this review focuses on invasive Typha in North America, the literature cited comes from research on Typha and other invasive species from around the world. As such, many of the underlying concepts in this review are relevant to invasive species in other wetland ecosystems worldwide

Bacterial response to dissolved organic matter affects resource availability for algae

In aquatic systems, the presence of colored dissolved organic matter (DOM) may affect algal growth in numerous ways. This paper focuses on the effects of DOM on resource availability. DOM contains nitrogen and phosphorus, which may become available following microbial or photochemical degradation. Also, addition of DOM may stimulate bacterial growth, which in turn may change the availability of nitrogen, phosphorus, and inorganic carbon to algae. Experiments conducted in a moderately colored lake showed that the effect of DOM on algal growth depended on the amount of nutrients present in the peat extract and on bacterial response to DOM. There was evidence for competition for phosphorus between algae and bacteria in some treatments. In addition, when both bacteria growth and algal growth were high, bacterial respiration of DOM alleviated algal carbon limitation by providing algae with an inorganic carbon source. Thus, the degree to which bacteria are stimulated by the addition of DOM will affect the amount of phosphorus and inorganic carbon available for algal growth. These results suggest that part of the difficulty in predicting algal response to changes in DOM and nutrient concentration may be due partially to variability in bacterial responses

Positive and negative effects of allochthonous dissolved organis matter and inorganic nutrients on phytoplankton growth

Dissolved organic matter can have both positive and negative effects on phytoplankton growth. Klug addresses the relative importance of the positive and negative effects of DOM extracts on phytoplankton growth