Aquatic systems are able to create a nexus of numerous ecosystem services, which are increasingly vulnerable to disturbances taking place in all compartments of the biosphere. Disturbance regimes are leading to fast and profound changes to the landscape with direct and indirect effects to adjacent water bodies. For example, human activities are increasingly altering aquatic ecosystems through direct changes in land use such as mining, urbanization, deforestation, agriculture, and infrastructure projects (eg. hydroelectric dams). Additionally, a variety of natural disturbances including abiotic (erosion, land-slides, wildfires, flooding, drought, hurricanes) and biotic origins (e.g.forest infestation/disease), which their regime and magnitude can also be altered by human/activities are also impacting terrestrial-aquatic linkages. These disturbances in the terrestrial environment are likely to impact the amount and quality of terrestrial materials as well as terrestrial microorganisms transported to nearby waters. Thus, the change in flux of carbon, nutrients, and other elements from land to aquatic ecosystems might, in turn, influence aquatic microbial communities and trophic interactions. However, to what extent all this may have consequences on the biogeochemical cycling, structure and functioning of aquatic ecosystems, is very poorly understood. This session invites any theoretical or empirical studies about the effects of landscape anthropogenic or natural disturbances (alone or in combination with other environmental disturbances) on freshwater and marine ecosystems, with focus on biogeochemical cycles and biological communities (metabolic activity, species composition and interactions). We aim at bridging the disconnect between terrestrial and aquatic processes across variable spatial and temporal scales and provide insight into the environmental, ecological, and social consequences of land effects on aquatic environments.
Lead Organizer: Bianca Rodríguez-Cardona, Université du Québec à Montréal (rodriguez.cardona.bm@gmail.com)
Co-organizers:
Michaela de Melo, Université du Québec à Montréal (michaelaldemelo@gmail.com)
João Henrique Amaral, University of Florida (jh.amaral@gmail.com)
Ada Pastor, Universitat de Girona (ada.pastor@udg.edu)
Clara Ruiz González, Institut de Ciències del Mar (clararg@icm.csic.es)
Presentations
03:00 PM
STREAM FUNCTIONAL RESPONSES TO LEGACY MINING IMPACTS (6189)
Primary Presenter: Alba Argerich, University of Missouri (argericha@missouri.edu)
This study focuses on the effects of legacy mining activities on the stream function of Lone Elm creek, an urban stream running through the city of Joplin, MO, USA. The area was once a major producer of lead and zinc and, although mining ceased during the second half of the 20th century, the impact of the activity can still be seen as the old mines are now flooded and discharge heavy-metal contaminated water to surface creeks. During nine months, we measured oxygen concentrations and water chemical parameters and performed nutrient additions above and below a mine-adit to understand the effects of this point discharge on stream functional process, specifically, stream metabolism and nutrient uptake. Continuous dissolved oxygen (DO) data revealed that the two reaches were characterized by different metabolic regimes. Results from constant-rate ammonium and phosphorus additions showed different controls on nutrient uptake between reaches: uptake in the upstream reach was largely influenced by seasonal patterns in primary producers, while the downstream reach was influenced by the elevated ammonium and iron concentrations from the mine adit. This study suggests that legacy mining activities continue to have significant ecological impacts even after mining has ceased and provides valuable information for understanding the impacts of legacy mining on ecosystem services that can be used to inform management and restoration efforts.
03:15 PM
LABILE CARBON AVAILABILITY INCREASES THE IN-STREAM NUTRIENT PROCESSING CAPACITY IN AN URBAN MEDITERRANEAN STREAM (5501)
Primary Presenter: David Pineda Morante, CEAB-CSIC (dpineda@ceab.csic.es)
Inputs from wastewater treatment plants (WWTP) increase nutrient loads in receiving streams, especially in Mediterranean regions due to low stream dilution. Further, these Mediterranean streams have a low capacity to reduce dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) excesses. We hypothesize that a low availability of labile carbon (C) can limit the heterotrophic activity of these streams; and thus, we expect that an increase in labile C will decrease DIN and SRP concentrations by promoting in-stream heterotrophic activity. We tested this hypothesis by adding a brewery by-product, as a source of labile C, to a WWTP-receiving stream and examining its effects on DIN (ammonium and nitrate) and SRP concentrations. We ran a 4-day C addition in a 180 meters reach of a forested headwater Mediterranean stream in July 2022, when 100% of the discharge was sourced by the WWTP effluent. We collected hourly water samples along the reach before and during the C addition. Diel oscillations of ammonium and nitrate concentrations together with longitudinal changes of both DIN and SRP forms during background conditions, suggest a high in-stream bioreactive capacity controlling nutrient concentrations. The in-stream capacity to process nutrients increased during the C addition, and the stream even shifted from being a source to a sink of DIN. Our results support the idea that the capacity of WWTP-receiving streams to mitigate nutrient loads is limited by the availability of labile C sources.
03:30 PM
HYPOTHESIS TESTING OF EUTROPHICATION DRIVERS USING THE LAKE SEDIMENT RECORD (7314)
Primary Presenter: Madeleine Moyle, University of Liverpool (maddy.moyle@liverpool.ac.uk)
Reliable quantification of phosphorus (P) sources is critical for cost effective mitigation of freshwater eutrophication. At present, measures to reduce nutrient loading to aquatic systems are widely predicated on the assumption that in the absence of sewage inputs, agricultural sources, particularly those that persist in the catchment as legacy P, are the primary control. For example, landscape export coefficient models assign particularly high values to arable land, implying that fertilizer application rates are a key control. Long duration records of lake water total phosphorus (TP) offer a solution; by comparison with historical records of potential drivers, assumptions over the relative importance of each source can be tested. However, most directly measured TP records are not long enough to enable this. Here, lake sediment-inferred TP records (SI-TP) offer an alternative. We combine a 200-year SI-TP record from Crose Mere, a small eutrophic UK lake, with historical land-use data to test the assumed dominance of arable P sources in the lake P budget. We find 20th century chemical fertilizer usage has no direct influence on TP trends, highlighting the canonical assumption about the role of chemical agriculture in driving freshwater eutrophication need not be valid. This paves the way for a critical analysis of eutrophication drivers, and a recognition that export coefficient models cannot reliably use single values to represent arable land. This approach enables the impact of land use change on the lake P cycle to be quantified, bridging the terrestrial-aquatic divide.
03:45 PM
PHOSPHORUS UPTAKE AND AQUATIC METABOLISM IN CONTIGUOUS REACHES OF A TROPICAL URBAN STREAM IN BRAZIL (5401)
Primary Presenter: João Miguel Merces Bega, Universidade de São Paulo - USP (joaobega@usp.br)
Streams interact closely with their drainage areas in a way that anthropogenic-induced shifts in the respective watersheds can dramatically impair their structure and functioning. This study aimed to assess metabolic rates (ecosystem respiration [ER] and gross primary production [GPP]) and soluble reactive phosphorus (SRP) ambient uptake metrics (length [Sw], velocity [Vf], and rate [U]) in two contiguous reaches (~ 500 m each) of a tropical urban stream (< 200 L s-1) under different typologies of anthropogenic impacts (R1 [natural substrate, preserved riparian vegetation, signs of erosion, and a meandering channel] and R2 [altered substrate, degraded riparian vegetation, erosive features, and wastewater inputs]). SRP uptake metrics and metabolic rates were obtained with tracer addition and whole-stream single-station methods, respectively, in six campaigns in 2022 (one every two months). Sw (65.3 [min.] - 985.1 [max.] [R1] and 779.5 – 2963.4 m [R2]) and Vf (1.9 – 41.6 and 0.8 – 4.7 mm min-1) were significantly different between reaches (p < 0.05, Wilcoxon test), while U (23.6 – 795.5 and 38.5 – 109.1 µg m-2 min-1), ER (0.45 – 10.35 and 5.82 – 14.04 g O2 m-2 d-1), and GPP (0.10 – 0.35 and 0.05 – 0.26 g O2 m-2 d-1) were not (p > 0.05). In conclusion, contiguous reaches can have great variability concerning nutrient uptake despite having similar metabolic rates. Although highly impacted urban reaches may retain some nutrient uptake ability, those better preserved will have more. Such spatial heterogeneity must be considered in further studies and monitoring of urban streams.
04:00 PM
INVESTIGATING THE COMBINED EFFECTS OF PLURI-DECADAL CO2 INCREASE AND RIVER INPUTS VARIABILITY ON BIVALVES CARBON STABLE ISOTOPE IN COASTAL ECOSYSTEMS (6041)
Primary Presenter: Camilla Liénart, University of Bordeaux (camilla.lienart@u-bordeaux.fr)
Coastal ecosystems connect land and sea through exchanges of material and energy, generating numerous ecosystem services. However, the biosphere at this interface is increasingly vulnerable to all the disturbances linked with climate change, including increased atmospheric CO2, changes in productivity base or altered carbon and nutrient fluxes from land to sea. As a result of fossil fuels burning, 13C/12C values of atmospheric CO2 are decreasing (i.e. the Suess effect). This decrease eventually reflects in the 13C/12C values of marine organism tissues, which can confound interpretation of e.g. organic carbon cycling, dietary carbon origin or food web dynamics. In a multi-ecosystem study, we measured spanning 1 to 4 decades the 13C/12C of bivalve tissues, often used as sentinel organisms for environmental change. Our 33 sites are distributed along the French littoral and encompassing a distance gradient from estuaries. We aimed to identify the Suess effect on bivalves and disentangle its signal from other environmental disturbances, especially terrestrial inputs from rivers. Across all sites, we observed a decrease of 0.1 to 1.0 ‰ per decade in 13C/12C bivalve tissues, with a generally less pronounced decrease for the sites close to estuarine mouths. We ultimately correlated 13C/12C values with environmental data, especially river inputs, which relate to the use and management of watersheds, in order to explain the 13C/12C patterns. Our results contribute to the understanding of the complex and interacting effects of human disturbances on coastal ecosystem functioning.
04:15 PM
Impact of lakeshore residential development on littoral habitat and fish communities: Insights from partially developed lakes (6521)
Primary Presenter: M. VANDER ZANDEN, University of Wisconsin - Madison (mjvanderzand@wisc.edu)
In many regions of the world, homebuilding and residential development is concentrated around lake shorelines. The impacts of lakeshore residential development on riparian and littoral habitats are well documented. Yet we have a poor understanding of how these human-driven habitat changes influence the biota such as nearshore fish communities. Here we compare developed and undeveloped stretches of shorelines in two lakes in which approximately half of the shoreline is developed, and the other half is undeveloped. This approach offers unique insights because comparisons are not confounded by underlying differences in fish communities among lakes. Comparing developed and undeveloped shorelines, there were no differences in sediment hardness, slope, and macrophyte biovolume. In contrast, there were strong differences in shoreland habitat and littoral coarse woody habitat. Path analysis revealed the direct and habitat-mediated effects of lakeshore residential development on nearshore fish communities. The overall effects of residential development on nearshore fish communities at the intra-lake scale were subtle. Our study adds to our understanding of the interactive effects of lakeshore residential development and habitat on biotic communities and highlights the importance of the scale of analysis for understanding these effects.
SS011E Aquatic Ecosystems in the Face of Landscape Disturbances: From Biological Communities to Biogeochemical Cycles
Description
Time: 3:00 PM
Date: 9/6/2023
Room: Auditorium Illes Balears