Contributed Session.
Lead Organizer: Meg Blome, East Carolina University (blomem19@ecu.edu)
Co-organizers:
James Wainaina, Woods Hole Oceanographic Institution (jwmbora@gmail.com)
Presentations
04:30 PM
Development and Diversity of Bacterial Biofilms in Response to Internal Tides (8721)
Primary Presenter: Fahad Al Senafi, Kuwait University (fahad.alsenafi@ku.edu.kw)
Information pertaining to changes in abundance and composition of microbial communities on offshore platforms in relation to changes in environmental conditions due to internal tides are scarce. In this study, artificial substrata were deployed at two locations on a gently sloping seabed off the coast of Kuwait. The abiotic factors at the two sites were recorded spatially and temporally using time-series measurements and continuous turbulence profiling for 13 days. Results showed variations in water density between the upper and deeper waters with the pycnocline undulating between 6 and 15 m depth at both locations. In the water layer beneath the pycnocline, significant current shear due to the internal tides led to higher turbidity coupled with lower dissolved oxygen (DO) and chlorophyll a concentration. The microbiological data showed a significant decrease in the biofilm total biomass, bacterial counts and phototrophic biomass with increase in depth at both locations. The 16S rRNA amplicon sequence analysis revealed that biofouling bacterial communities were affected by depth with Alphaproteobacteria and Bacteroidetes members dominating the upper and deeper waters at both locations. The non-metric multidimensional scaling (NMDS) based-ordination analysis revealed that biofouling bacterial communities at 3 m were different than at 15 m, with a percentage of shared operational taxonomic units (OTUs) ≤64% between locations and depths. The power of the employed system is demonstrated in the results that shed light on the significance of prevailing environmental conditions associated with internal tides in shaping the biofilm community in subtropical offshore water systems.
04:45 PM
The swimming performance and genomic insights into diverse bacterial taxa and brain transcriptome in grass carp induced by water flow stress (8790)
Primary Presenter: Mian Adnan, China Three Gorges University (zoology863@gmail.com)
Water flow velocity plays a crucial role in shaping the physiological performance and genetic responses of aquatic species. Additionally, the high-water flow stress could potentially affect the fish swimming behavior, which is an important factor for fish swimming behavior. Therefore, in this study the impact of water flow stress on fish swimming performance, genomic insights associated with intestinal bacterial communities, alongside brain transcriptome was observed. A total of 40 healthy Ctenopharyngodon idella were selected and divided into four groups. Firstly, each group was exposed to different water velocities (Low 0.5 BL/s; Medium 1.5 BL/s, and High 2.0 BL/s) for two hours per day for five days respectively. The water velocity induced fish were further transferred into normal tanks (0.0 BL/s) for further studies. Additionally, the swimming performance was checked, which showed a significant reduction in swimming performance in the high-water velocity induced group (p < 0.05). Moreover, 16s rRNA sequencing revealed that the water flow stress significantly increased the potential pathogenic bacteria such Aeromonas and Vibrio (p < 0.05), which could further hinder the fish immunity of fish resulting in a decrease in swimming performance. The transcriptome additionally confirmed the regulation of immune response genes (p < 0.05) and some enrichment pathways including behavior (p < 0.05***), skeletal system development (p < 0.05***), hormone activity (p < 0.05***), muscle contraction (p < 0.05**), locomotion (p < 0.05*), and swim bladder development (p < 0.05*) in velocity induced groups, which could potentially play a role in fish swimming behavior. The current study could significantly highlight the importance of integrating fish physiology, microbiome research, and brain transcriptome to better understand how environmental stressors influence aquatic species in rapidly changing ecosystems, global warming, climate change and human induced activities.
05:00 PM
Integrating Phytoplankton Genomics and Remote Sensing to Detect Iron Stress from Space (9348)
Primary Presenter: Amy Nuno, University of California, Irvine (anunopug@uci.edu)
Iron stress is a critical factor in biological oceanography, constraining the growth of primary productivity in an estimated 60% of the global surface ocean. Phytoplankton become iron stressed when the iron to nitrogen supply ratio is low. Conditions likely to induce iron stress in phytoplankton include low aeolian dust deposition and/ or high vertical mixing, both of which vary across time and space. However, only a few studies focus on the spatial and temporal of iron stress outside of HNLC regions. This gap limits our ability to fully assess the dynamics of global phytoplankton iron stress. The satellite-derived fluorescence quantum yield (Φsat), a spatial-temporal dataset spanning 20+ years derived from MODIS-Aqua, provides insight into phytoplankton iron stress through their photosynthetic physiological responses. The integration of genomics can validate Φsat primarily as an iron stress indicator. This validation allows us to assess the global spatial and temporal distribution of iron stress beyond the well-known HNLC regions. Thus far the derivation of the Φsat signal has been updated and reassessed using the latest 2022 reprocessed MODIS data. We integrated in-situ hydrography and genomic measurements with satellite remote sensing to quantify the global contemporary variation in iron stress. Results show that Φsat and in-situ genomic iron stress biomarkers have a positive correlation. Also, that Φsat and community Earth System Models iron stress models have a positive correlation. Our validation results indicate that Φsat is a measurement of iron stress. Furthermore, spatial-temporal evaluations show that Φsat is elevated in well-known High Nutrient Low Chlorophyll (HNLC) regions. In addition, Φsat is elevated seasonally in the North Atlantic spring and Indian Ocean summer. The long-term trends of Φsat show a prominent decreasing iron stress trend in gyre regions. The Φsat validation has allowed us to assess the global spatial and temporal distribution of iron stress beyond the well-known HNLC regions.
05:15 PM
NITROUS OXIDE PRODUCTION BY PHOTOCHEMODENITRIFICATION IN POLAR AND TROPICAL MARINE WATERS (9509)
Primary Presenter: Elizabeth Leon-Palmero, Princeton University (el23@princeton.edu)
Nitrous oxide (N2O) is the main stratospheric ozone-depleting agent and a powerful greenhouse gas. Ammonia oxidizers and denitrifiers are microbial groups that are thought to control the N2O budget in aquatic systems. Recently, a novel abiotic process known as photo(chemo)denitrification (PCD) has been identified as a significant contributor to N2O production. It consists of photochemical reduction of nitrite and photoreduced nitrate to N2O, and occurs at the oxic surface of freshwater and marine environments. Because it takes place at the water-air interface, PCD has the potential to contribute substantially to N2O emissions. However, there were no measurements of PCD rates in the open ocean and at higher latitudes, which prevents evaluating the importance of PCD in the global ocean. Here, we quantified N2O production by PCD and microbial sources in surface oxic waters from the coast of West Greenland (70oN), and in the Eastern Tropical South Pacific Ocean (ETSP, 14-22oS) using 15N-labelled tracer experiments. We detected PCD at both sites, at rates exceeding biological N2O production in surface waters. Even at polar latitudes, sunlight is bright enough to drive PCD, at least during the summer period. At latitudes closer to the equator, with much more intense solar radiation, the PCD N2O production rates may be comparable to N2O production rates occurring in deeper layers due to biological activity. These new findings have critical implications for the global N2O budget, suggesting that N2O production in aquatic systems would be underestimated if PCD is not considered.
05:30 PM
PREVALENCE AND DRIVERS OF OXYGEN SUPERSATURATION IN DEEP WATERS OF GLOBAL LAKES (8987)
Primary Presenter: Stephen Jane, University of Notre Dame (coachman7777@yahoo.com)
Warming of surface waters is associated with declining oxygen concentrations in lake bottom waters, reducing habitat availability for oxygen sensitive cold-water species and altering biogeochemistry. Amidst this backdrop, identifying lake features that may confer some resistance to oxygen loss is imperative. Oxygen supersaturation represents oxygen concentrations exceeding those expected for a given water temperature and atmospheric pressure. Supersaturation is often associated with gross primary production exceeding oxygen consumption by respiration and therefore may indicate resistance to oxygen loss. We used a database of 2,822 lakes across mostly North America and Europe to examine the prevalence and drivers of oxygen supersaturation below the surface mixed layer. We find deep-water supersaturation is most common at the top of the metalimnion, present in > 40% of profiles across lakes having a metalimnion. In the hypolimnion, supersaturation is uncommon, occurring in < 5% of profiles across a representative sample of US lakes. Because the top of the metalimnion can often be relatively warm, hypolimnetic supersaturation may hold more potential for preserving oxythermal habitat for cold-water species. Deep-water supersaturation was most likely in lakes having both low nutrient and dissolved organic matter concentrations. In dystrophic lakes approaching 25 mg/L dissolved organic carbon, the probability of deep-water supersaturation approached 0. Our findings provide a framework for pinpointing lakes likely to better maintain deep-water oxygen as deoxygenation progresses.
CS08 - Global Oceanography and Limnology
Description
Time: 4:30 PM
Date: 29/3/2025
Room: W206A