Implications of the meteoric rise in atmospheric CO2 concentrations on natural and human systems are far reaching. It is imperative that CO2 emissions are reduced, but even the most optimistic scenarios for future emissions indicate mitigation will be required (e.g. carbon capture) and that the natural ecosystems and food supply systems critical to human wellbeing will be impacted. Global macroalgal and macrophyte health and resilience is central to a healthy planet. Macroalgae and macrophytes are at the nexus of the climate crisis as they are both vulnerable to climate change and have roles to play in delivering a sustainable future. Not only are they foundational species in the aquatic environment, oxygenating surface waters, providing habitat structure and fueling higher trophic level organisms, but they also provide humans with ecosystem services including carbon sequestration/removal, sources of human nutrition, animal feed, and biofuels. However, macroalgae and macrophytes are particularly vulnerable to climate change and environmental degradation. For example, crustose coralline and fleshy macroalgal species alike are distributed across the globe from the tropics through the high Arctic, including some of the fastest changing ecosystems on earth. As aquatic environments change, the fate of these communities, the ecosystems they support, and the carbon they sequester is poorly understood. Plants and algae can also tell us about past climate and their own history, to offer clues about our shared future. For example, past environmental variability (e.g., in temperature and sea-ice extent) can be reconstructed using macroalgae by investigating the growth and chemical makeup of long-lived marine coralline algae. The variations in these species’ distributions and physiologies through time as climate changed also offer insight into how they may respond to ongoing climate change. This session welcomes research across all macroalgae (including fleshy and coralline species) and macrophyte species, from all geographies (tropical to Arctic and marine to fresh water), and all perspectives concerning macroalgae and macrophytes in a changing world. Examples of topics welcomed include (i) the effects of environmental variability on macroalgal and macrophyte growth and biogeography, (ii) implications of change on coralline algal growth for reconstruction of the environment, (iii) macroalgal and macrophyte cultivation and associated applications – aquaculture, human consumption, biofuels, animal feed, and carbon dioxide reduction/sequestration (CDR) (iv) remote sensing, monitoring, and mapping of productivity. We hope this session will improve collaboration across disciplines within and between the macroalgal and macrophyte research community and accelerate our ability to understand, protect, and harness aquatic macro-photosynthesizers as we seek to build the good, sustainable Anthropocene.
Lead Organizer: Jessica Gould, Northeastern University (jlagould@gmail.com)
Co-organizers:
Natasha Leclerc, University of Toronto (natasha.leclerc@mail.utoronto.ca)
Tom Bell, WHOI (tbell@whoi.edu)
Aron Stubbins, Northeastern University (a.stubbins@northeastern.edu)
Presentations
02:00 PM
MULTIDECADAL REMOTE SENSING OF KELP FORESTS IN ARGENTINA (7925)
Primary Presenter: Ashland Aguilar, Woods Hole Oceanographic Institution (aguilar.as@northeastern.edu)
In recent years, satellite imagery has been utilized to monitor the dynamics of kelp forest canopies across vast temporal and spatial scales. Previous research has focused heavily on Eastern Pacific Ocean coastlines in the northern hemisphere, despite the southern hemisphere having highly productive and abundant kelp forests. Even though the coast of Argentina is home to some of the largest Macrocystis pyrifera kelp forests in the world, there have been few long term studies in Argentina due to its vast remote coastlines, making satellite imagery an invaluable research tool. Landsat satellite imagery was utilized to gather long term data (40 years) across three Argentinian provinces; Chubut, Santa Cruz, and Tierra del Fuego. Given the high variability of kelp forests, long-term data is necessary to elucidate patterns and environmental drivers that are influencing their abundance and distribution. This study found that Santa Cruz and Tierra del Fuego provinces have the largest kelp habitat, and Chubut and Tierra del Fuego provinces showed significant increases in kelp forest canopy area over decadal timescales. Additionally, we found the Antarctic Oscillation (AAO) to be significantly related to kelp forest canopy dynamics in Santa Cruz and Tierra del Fuego provinces. This study provides valuable insight on the size, location, and dynamics of kelp forest ecosystems to inform future conservation efforts.
02:15 PM
PHYSIOLOGICAL RESPONSES OF INTERTIDAL MACROALGAE TO OCEAN AND ATMOSPHERIC WARMING (7838)
Primary Presenter: Rosa Chefaoui, Universidad Rey Juan Carlos (rosa.chefaoui@urjc.es)
The biological assemblages of European temperate coasts show significant climate change impacts, and several canopy-forming algae with their southern limit in the NW Iberian Peninsula are experiencing range contractions. We investigate the thermal responses of two brown algae species, both distributed along the Eastern North Atlantic coast and sharing similar distribution patterns, that differ in their intertidal positions: Pelvetia canaliculata (upper intertidal) and Fucus serratus (lower intertidal). We also explored phenotypic/adaptive differences in thermal response between the southernmost (NW Iberian Peninsula) and northern populations (Scotland) of the species. By means of physiological experiments in mesocosms and air chambers we investigated how a gradient of 12 sea surface temperature and 2 air temperature treatments affect the growth and mortality of these algae. We applied chlorophyll fluorescence (Imaging Pam), respirometry, and C:N ratio analyses to estimate the combined effects of temperature and desiccation. The results of our ecophysiological experiments will allow us to infer local extinctions and drastic modifications in intertidal communities in response to climate change.
02:30 PM
TRAIT RESPONSES OF BRACKISH WATER MACROPHYTE TO CLIMATE WARMING THROUGH TWO SYNCHRONIZED MESOCOSM EXPERIMENTS IN DIFFERENT CLIMATE REGIONS (8304)
Primary Presenter: Md Masum Billah, Middle East Technical University (METU), Turkey (masum_imsf07@yahoo.com)
Submerged macrophytes play a crucial role as primary producers, contributing essential ecosystem functions and services. Our study aimed to assess the effects of projected climate warming (4.5 °C) on the traits of a submerged aquatic macrophyte (Stuckenia pectinata) under brackish lake conditions (4 ppt) in two distinct climatic regions of Turkey: a cold semi-arid climate in Ankara and a hot, dry Mediterranean climate in Mersin, employing a mesocosm experiment. The mesocosms were inoculated with natural communities at trophic levels from plankton to fish and Stuckenia pectinata was used as a model species due to its widespread distribution in brackish lakes in the region. Plant morphological and physiological traits, including plant height, canopy height, number of leaves per shoot, percentage of leaves undergoing senescence, biomass ratio (dry weight/wet weight, DW:WW), epiphytic algal biomass, leaves’ chlorophyll-a and b, and leaves/shoot C and N content, were considered during the study. Results indicated significant variations in plant canopy height, biomass ratio, number of leaves, and epiphytic algal biomass between two climate regions. Overall, our data indicated that this species exhibited resilience to the anticipated 4.5 °C warming. The noticeable variations in biomass dry matter content (indicated with wet mass and DW:WW) between two climate regions may carry significant implications for ecosystem functioning such as animal grazing and/or decompositions.
02:45 PM
Biofiltering function of macrophytes for a potentially toxic elements cycles in aquatic systems (8446)
Primary Presenter: Galina Shinkareva, Illinois State University (galina1989@yahoo.com)
The removal of toxic elements from freshwaters is challenging. Among the crucial agents facilitating water purification, macrophytes stand out as significant contributors. This study examines the Selenga River delta, one of the largest freshwater deltas that serves as a buffer for Lake Baikal from mining and urban activities in the watershed. We conducted summer field campaigns in 2011-2013 and 2017-2019, when water, suspended and bottom sediments, and macrophytes (Phragmites australis, Nuphar pumila, Ceratophyllum demersum) were sampled. Potentially toxic elements (PTEs) concentrations were analyzed in all samples using ICP-MS and ICP-AES methods at “VIMS” Institute (Moscow). Bioconcentration Factors (BCF) indicating the PTEs accumulation in aquatic plants, calculated in relation to the PTEs content in suspended and bottom sediments, and river water revealed that plants exhibit the highest accumulation rates for dissolved PTEs, while BCF values for suspended and bottom sediments were lower. Coastal Phragmites australis and submerged Ceratophyllum demersum had higher BCF levels relative to dissolved PTEs than floating Nuphar pumila. Our study demonstrates the crucial contribution of macrophyte species in accumulation of pollutants originating from upstream sources in the delta region. Combining these findings with the application of remote sensing methods to evaluate the spatial distribution of macrophyte species improves our comprehension of sedimentation patterns and the capacity of macrophytes to intercept PTEs fluxes in the deltaic ecosystems.
03:00 PM
Watershed land use is a primary driver of submersed aquatic plant community dynamics in the Upper Midwest (7739)
Primary Presenter: Jake Walsh, University of Minnesota-Twin Cities (jransom.walsh@gmail.com)
General understanding of submersed aquatic plant community responses to ecological change has been limited by data availability at broad scales. We used a 6,000 point intercept (PI) survey dataset to understand the lake- and watershed-level drivers of aquatic plant dynamics in Minnesota and Wisconsin (USA). We built annual taxonomic inventories from lakes with at least 10 years of PI data (41 lakes and 588 lake years from 2000-2022) and quantified community taxonomic richness, turnover rates, covariance, synchrony, directional compositional change, and stability over time. We fit structural equation models to investigate lake- and watershed-level drivers of these metrics. Models explained between 26% and 64% of the variation in each metric. We found that percent land cover that was agricultural or developed was the primary driver of community dynamics. Percent agricultural or developed cover was negatively related to taxonomic richness, was the primary driver of directional change in community composition and was negatively related to shifts in taxonomic rank abundance. It also influenced other lake-level drivers as it was negatively associated with water clarity and positively associated with invasion status. Lake area, shoreline development factor, and invasion status influenced at least one metric, while water clarity and the abundance of lakes, streams and wetlands in the watershed influenced none. The outsized importance of watershed land use is notable, suggesting that watershed-level management could benefit submersed taxonomic richness and community composition.
03:15 PM
PHYTOTOXIC HYDROGEN SULFIDE DOES NOT EXPLAIN VARIATION IN RESPONSES OF SEAGRASS AND MACROALGAL COMMUNITY COMPOSITION TO GREEN TURTLE GRAZING (7857)
Primary Presenter: Robert Johnson, University of Wisconsin-Madison (robert.a.johnson@wisc.edu)
Green turtles (Chelonia mydas) are marine herbivores that consume seagrass for their diet, and whose grazing strategy can alter floral community composition in seagrass habitats. Responses to grazing vary among meadows, but the drivers of this variability are not well understood. Hydrogen sulfide (H2S) is a phytotoxin produced via sulfate reduction that can limit plant growth at high concentrations and may be mediated by grazing-induced changes in seagrass metabolism. To investigate if grazing-induced differences in sediment sulfur (S) dynamics could explain variability in floral species composition, we surveyed seagrass meadows with and without active green turtle grazing along Florida’s west coast. Across sites, there was a trend for higher seagrass and algal species richness in areas grazed by turtles. However, while concentrations of both sediment porewater H2S (range 1-1388 uM) and reducible inorganic S (range 0.9-15.3 umol S g-1 sediment) varied across sites, neither differed consistently between grazed and ungrazed meadows, suggesting that factors other than, or in addition to, sediment S dynamics may be important in driving responses of the seagrass floral community to grazing. Given increasing green turtle abundance with successful conservation efforts in recent decades, our findings highlight the need for a better understanding of the drivers of variability in seagrass and algal communities across meadows grazed by green turtles.
SS33A - Macroalgae and Macrophytes in a Changing World
Description
Time: 2:00 PM
Date: 6/6/2024
Room: Meeting Room KL