Teasing apart the host-related, nutrient-related and temperature-related effects shaping the phenology and microbiome of the tropical seagrass Halophila stipulacea

2021 ◽  
Author(s):  
Amir Szitenberg ◽  
Pedro Beca-Carretero ◽  
Tomás Azcárate-García ◽  
Timur Yergaliyev ◽  
Rivka Alexander-Shani ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Nutrient Loading ◽  
Field Studies ◽  
Nutrient Stress ◽  
Stress Factors ◽  
Gulf Of Aqaba ◽  
Nutrient Concentrations ◽  
Host Diversity ◽  
Seagrass Meadows ◽  
Halophila Stipulacea

Background: Halophila stipulacea seagrass meadows are an ecologically important and threatened component of the ecosystem in the Gulf of Aqaba. Recent studies have demonstrated correlated geographic patterns for leaf endophytic community composition and leaf morphology, also coinciding with different levels of water turbidity and nutrient concentrations. Based on these observations, workers have suggested an environmental microbial fingerprint, which may reflect various environmental stress factors seagrasses have experienced, and may add a holobiont level of plasticity to seagrasses, assisting their acclimation to changing environments and through range expansion. However, it is difficult to tease apart environmental effects from host-diversity dependent effects, which have covaried in field studies, although this is required in order to establish that differences in microbial community compositions among sites are driven by environmental conditions rather than by features governed by the host. Results: In this study we carried out a mesocosm experiment, in which we studied the effects of warming and nutrient stress on the composition of epiphytic bacterial communities and on some phenological traits. We studied H. stipulacea collected from two different meadows in the Gulf of Aqaba, representing differences in the host and the environment alike. We found that the source site from which seagrasses were collected was the major factor governing seagrass phenology, although heat increased shoot mortality and nutrient loading delayed new shoot emergence. Bacterial diversity, however, mostly depended on the environmental conditions. The most prominent pattern was the increase in Rhodobacteraceae under nutrient stress without heat stress, along with an increase in Microtrichaceae. Together, the two taxa have the potential to maintain nitrate reduction followed by an anammox process, which can together buffer the increase in nutrient concentrations across the leaf surface. Conclusions: Our results thus corroborate the existence of environmental microbial fingerprints, which are independent from the host diversity, and support the notion of a holobiont level plasticity, both important to understand and monitor H. stipulacea ecology under the changing climate.

scholarly journals Nutrient History Affects the Response and Resilience of the Tropical Seagrass Halophila stipulacea to Further Enrichment in Its Native Habitat

2021 ◽  
Vol 12 ◽  
Author(s):  
Stephanie B. Helber ◽  
Gidon Winters ◽  
Marleen Stuhr ◽  
E. F. Belshe ◽  
Stefanie Bröhl ◽  
...  
Keyword(s):  
Marine Protected Area ◽  
Nutrient Stress ◽  
Interactive Effects ◽  
Gulf Of Aqaba ◽  
Individual Plant ◽  
Seagrass Species ◽  
Area Index ◽  
Seagrass Meadows ◽  
Halophila Stipulacea

Eutrophication is one of the main threats to seagrass meadows, but there is limited knowledge on the interactive effects of nutrients under a changing climate, particularly for tropical seagrass species. This study aimed to detect the onset of stress in the tropical seagrass, Halophila stipulacea, by investigating the effect of in situ nutrient addition during an unusually warm summer over a 6-month period. We measured a suite of different morphological and biochemical community metrics and individual plant traits from two different sites with contrasting levels of eutrophication history before and after in situ fertilization in the Gulf of Aqaba. Nutrient stress combined with summer temperatures that surpassed the threshold for optimal growth negatively affected seagrass plants from South Beach (SB), an oligotrophic marine protected area, while H. stipulacea populations from North Beach (NB), a eutrophic and anthropogenically impacted area, benefited from the additional nutrient input. Lower aboveground (AG) and belowground (BG) biomass, reduced Leaf Area Index (LAI), smaller internodal distances, high sexual reproductive effort and the increasing occurrence of apical shoots in seagrasses from SB sites indicated that the plants were under stress and not growing under optimal conditions. Moreover, AG and BG biomass and internodal distances decreased further with the addition of fertilizer in SB sites. Results presented here highlight the fact that H. stipulacea is one of the most tolerant and plastic seagrass species. Our study further demonstrates that the effects of fertilization differ significantly between meadows that are growing exposed to different levels of anthropogenic pressures. Thus, the meadow’s “history” affects it resilience and response to further stress. Our results suggest that monitoring efforts on H. stipulacea populations in its native range should focus especially on carbohydrate reserves in leaves and rhizomes, LAI, internodal length and percentage of apical shoots as suitable warning indicators for nutrient stress in this seagrass species to minimize future impacts on these valuable ecosystems.

scholarly journals From coast to coast to coast: ecology and management of seagrass ecosystems across Canada

FACETS ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 139-179
Author(s):  
Grace E.P. Murphy ◽  
Jillian C. Dunic ◽  
Emily M. Adamczyk ◽  
Sarah J. Bittick ◽  
Isabelle M. Côté ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Human Activities ◽  
Nutrient Loading ◽  
Human Impacts ◽  
Coastal Development ◽  
Seagrass Meadows ◽  
The Pacific ◽  
Wide Range ◽  
Seagrass Ecosystems ◽  
Plant Habitat

Seagrass meadows are among the most productive and diverse marine ecosystems, providing essential structure, functions, and services. They are also among the most impacted by human activities and in urgent need of better management and protection. In Canada, eelgrass ( Zostera marina) meadows are found along the Atlantic, Pacific, and Arctic coasts, and thus occur across a wide range of biogeographic conditions. Here, we synthesize knowledge of eelgrass ecosystems across Canada’s coasts, highlighting commonalities and differences in environmental conditions, plant, habitat, and community structure, as well as current trends and human impacts. Across regions, eelgrass life history, phenology, and general species assemblages are similar. However, distinct regional differences occur in environmental conditions, particularly with water temperature and nutrient availability. There is considerable variation in the types and strengths of human activities among regions. The impacts of coastal development are prevalent in all regions, while other impacts are of concern for specific regions, e.g., nutrient loading in the Atlantic and impacts from the logging industry in the Pacific. In addition, climate change represents a growing threat to eelgrass meadows. We review current management and conservation efforts and discuss the implications of observed differences from coast to coast to coast.

scholarly journals Does Warming Enhance the Effects of Eutrophication in the Seagrass Posidonia oceanica?

2020 ◽  
Vol 7 ◽  
Author(s):  
Jessica Pazzaglia ◽  
Alex Santillán-Sarmiento ◽  
Stephanie B. Helber ◽  
Miriam Ruocco ◽  
Antonio Terlizzi ◽  
...  
Keyword(s):  
Multiple Stressors ◽  
Posidonia Oceanica ◽  
Stress Factors ◽  
Nutrient Concentrations ◽  
Additional Stress ◽  
Cultural Eutrophication ◽  
Seagrass Meadows ◽  
Increased Temperature ◽  
The Impact

Seagrass meadows are disappearing at rates comparable to those reported for mangroves, coral reefs, and tropical rainforests. One of the main causes of their decline is the so-called cultural eutrophication, i.e., the input of abnormal amounts of nutrients derived from human activities. Besides the impact of eutrophication at a local scale, the occurrence of additional stress factors such as global sea warming may create synergisms in detriment of seagrass meadows’ health. In the present study, we aimed to evaluate if plants undergoing chronic cultural eutrophication and plants growing in relatively pristine waters are more (or less) sensitive to heat stress, nutrient load and the combination of both stressors. To address this question, a mesocosm experiment was conducted using Posidonia oceanica collected from two environments with different nutrients load history. Plants were exposed in controlled conditions to high nutrient concentrations, increased temperature and their combination for 5 weeks, to assess the effect of the single stressors and their interaction. Our results revealed that plants experiencing chronic cultural eutrophication (EU) are more sensitive to further exposure to multiple stressors than plants growing in oligotrophic habitats (OL). OL and EU plants showed different morphological traits and physiological performances, which corroborates the role of local pressures in activating different strategies in response to global environmental changes. EU-plants appeared to be weaker during the treatments, showing the greatest percentage of mortality, particularly under increased temperature. Temperature and nutrient treatments showed opposite effects when tested individually and an offset response when combined. The activation of physiological strategies with high energetic expenses to cope with excess of nutrients and other stressors, could affect plants present and future persistence, particularly under eutrophic conditions. Our results represent a step forward in understanding the complex interactions that occur in natural environments. Moreover, unraveling intraspecific strategies and the role of local acclimation/adaptation in response to multiple stressors could be crucial for seagrass conservation strategies under a climate change scenario.

Loading rates of nutrients discharging from a golf course and a neighboring forested basin

1999 ◽  
Vol 39 (12) ◽  
pp. 99-107 ◽  
Author(s):  
Takao Kunimatsu ◽  
Miki Sudo ◽  
Takeshi Kawachi
Keyword(s):  
Nutrient Loading ◽  
Chamaecyparis Obtusa ◽  
Phosphorus Loading ◽  
Golf Course ◽  
Nutrient Concentrations ◽  
Golf Courses ◽  
Japanese Cypress ◽  
Arithmetic Average ◽  
Loading Rates ◽  
Runoff Rate

In the last ten years, the number of golf courses has been increasing in some countries as the game gains popularity. This indicates, a need to estimate the nutrient loading from golf courses in order to prevent the eutrophication of water bodies. Nutrient concentrations and flow rates of a brook were measured once a week from 1989 to 1990 at two sites: Site A of a brook flowing out from D-golf course (53 ha) and Site B of the same brook discharging into the golf course from an upper forested basin (23 ha) covered mainly with planted Japanese cypress (Chamaecyparis obtusa SIEB. et ZUCC). The bedrock of the area was granite. The annual values of precipitation and mean temperature were 1947 mm and 13.5°C in 1989, respectively. The arithmetic average values of discharge from the forested basin and the golf course were 0.392 and 1.26 mg/l total nitrogen (TN), 0.0072 and 0.145 mg/l total phosphorus (TP), 0.82 and 3.53 mg/l potassium ion (K+, 5.92 and 8.24 mg/l sodium ion (Na+), 2.1 and 9.9 mg/l suspending solid (0.001–2.0 mm, SS), 0.087 and 0.147 mS/cm electric conductivity (EC), and 0.031 and 0.037 m3/km2•s specific discharge, respectively. The loading rates of the forested basin and the golf course were 5.42 and 13.5 TN, 0.133 and 3.04 TP, 8.84 and 33.9 K+, 55.0 and 73.0 Na+, and 54.3 and 118 SS in kg/ha•y. The leaching and runoff rate of nitrogen in the chemical fertilizers applied on the golf course was calculated as 32%. These results indicated the importance of controlling the phosphorus loading for the management of golf courses.

scholarly journals A Model Study on the Role of Wetland Zones in Lake Eutrophication and Restoration

2001 ◽  
Vol 1 ◽  
pp. 605-614 ◽  
Author(s):  
J.H. Janse ◽  
W. Ligtvoet ◽  
S. Van Tol ◽  
A.H.M. Bresser
Keyword(s):  
Nutrient Loading ◽  
Predatory Fish ◽  
Nutrient Concentrations ◽  
Fish Stock ◽  
Mixing Rate ◽  
Marsh Vegetation ◽  
Model Calculations ◽  
Critical Loading ◽  
Marsh Area

Shallow lakes respond in different ways to changes in nutrient loading (nitrogen, phosphorus). These lakes may be in two different states: turbid, dominated by phytoplankton, and clear, dominated by submerged macrophytes. Both states are self-stabilizing; a shift from turbid to clear occurs at much lower nutrient loading than a shift in the opposite direction. These critical loading levels vary among lakes and are dependent on morphological, biological, and lake management factors. This paper focuses on the role of wetland zones. Several processes are important: transport and settling of suspended solids, denitrification, nutrient uptake by marsh vegetation (increasing nutrient retention), and improvement of habitat conditions for predatory fish. A conceptual model of a lake with surrounding reed marsh was made, including these relations. The lake-part of this model consists of an existing lake model named PCLake[1]. The relative area of lake and marsh can be varied. Model calculations revealed that nutrient concentrations are lowered by the presence of a marsh area, and that the critical loading level for a shift to clear water is increased. This happens only if the mixing rate of the lake and marsh water is adequate. In general, the relative marsh area should be quite large in order to have a substantial effect. Export of nutrients can be enhanced by harvesting of reed vegetation. Optimal predatory fish stock contributes to water quality improvement, but only if combined with favourable loading and physical conditions. Within limits, the presence of a wetland zone around lakes may thus increase the ability of lakes to cope with nutrients and enhance restoration. Validation of the conclusions in real lakes is recommended, a task hampered by the fact that, in the Netherlands, many wetland zones have disappeared in the past.

scholarly journals Nutrient Atmospheric Deposition on Utah Lake: A Comparison of Sampling and Analytical Methods

Hydrology ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 123
Author(s):  
Seth Michael Barrus ◽  
Gustavious Paul Williams ◽  
A. Woodruff Miller ◽  
M. Brett Borup ◽  
LaVere B. Merritt ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
Nutrient Loading ◽  
Inorganic Nitrogen ◽  
Dissolve Inorganic Nitrogen ◽  
Nutrient Concentrations ◽  
Nutrient Loads ◽  
Total Load ◽  
Significant Difference ◽  
Utah Lake ◽  
Collection Methods

We describe modified sampling and analysis methods to quantify nutrient atmospheric deposition (AD) and estimate Utah Lake nutrient loading. We address criticisms of previous published collection methods, specifically collection table height, screened buckets, and assumptions of AD spatial patterns. We generally follow National Atmospheric Deposition Program (NADP) recommendations but deviate to measure lake AD, which includes deposition from both local and long-range sources. The NADP guidelines are designed to eliminate local contributions to the extent possible, while lake AD loads should include local contributions. We collected side-by-side data with tables at 1 m (previous results) and 2 m (NADP guidelines) above the ground at two separate locations. We found no statistically significant difference between data collected at the different heights. Previous published work assumed AD rates would decrease rapidly from the shore. We collected data from the lake interior and show that AD rates do not significantly decline away from the shore. This demonstrates that AD loads should be estimated by using the available data and geostatistical methods even if all data are from shoreline stations. We evaluated screening collection buckets. Standard unscreened AD samples had up to 3-fold higher nutrient concentrations than screened AD collections. It is not clear which samples best represent lake AD rates, but we recommend the use of screens and placed screens on all sample buckets for the majority of the 2020 data to exclude insects and other larger objects such as leaves. We updated AD load estimates for Utah Lake. Previous published estimates computed total AD loads of 350 and 153 tons of total phosphorous (TP) and 460 and 505 tons of dissolve inorganic nitrogen (DIN) for 2017 and 2018, respectively. Using updated collection methods, we estimated 262 and 133 tons of TP and 1052 and 482 tons of DIN for 2019 and 2020, respectively. The 2020 results used screened samplers with lower AD rates, which resulted in significantly lower totals than 2019. We present these modified methods and use data and analysis to support the updated methods and assumptions to help guide other studies of nutrient AD on lakes and reservoirs. We show that AD nutrient loads can be a significant amount of the total load and should be included in load studies.

scholarly journals Modelling the biogeochemical effects of heterotrophic and autotrophic N<sub>2</sub> fixation in the Gulf of Aqaba (Israel), Red Sea

2018 ◽  
Vol 15 (24) ◽  
pp. 7379-7401 ◽  
Author(s):  
Angela M. Kuhn ◽  
Katja Fennel ◽  
Ilana Berman-Frank
Keyword(s):  
Water Column ◽  
Red Sea ◽  
N2 Fixation ◽  
Large Scale ◽  
Gulf Of Aqaba ◽  
Nutrient Concentrations ◽  
Nutrient Ratios ◽  
Biogeochemical Models ◽  
Deep Waters ◽  
Direct Measurements

Abstract. Recent studies demonstrate that marine N2 fixation can be carried out without light by heterotrophic N2 fixers (diazotrophs). However, direct measurements of N2 fixation in aphotic environments are relatively scarce. Heterotrophic as well as unicellular and colonial photoautotrophic diazotrophs are present in the oligotrophic Gulf of Aqaba (northern Red Sea). This study evaluates the relative importance of these different diazotrophs by combining biogeochemical models with time series measurements at a 700 m deep monitoring station in the Gulf of Aqaba. At this location, an excess of nitrate, relative to phosphate, is present throughout most of the water column and especially in deep waters during stratified conditions. A relative excess of phosphate occurs only at the water surface during nutrient-starved conditions in summer. We show that a model without N2 fixation can replicate the observed surface chlorophyll but fails to accurately simulate inorganic nutrient concentrations throughout the water column. Models with N2 fixation improve simulated deep nitrate by enriching sinking organic matter in nitrogen, suggesting that N2 fixation is necessary to explain the observations. The observed vertical structure of nutrient ratios and oxygen is reproduced best with a model that includes heterotrophic as well as colonial and unicellular autotrophic diazotrophs. These results suggest that heterotrophic N2 fixation contributes to the observed excess nitrogen in deep water at this location. If heterotrophic diazotrophs are generally present in oligotrophic ocean regions, their consideration would increase current estimates of global N2 fixation and may require explicit representation in large-scale models.

scholarly journals Assessing the Eutrophic Susceptibility of New Zealand Estuaries

2020 ◽  
Vol 43 (8) ◽  
pp. 2015-2033 ◽  
Author(s):  
David R. Plew ◽  
John R. Zeldis ◽  
Bruce D. Dudley ◽  
Amy L. Whitehead ◽  
Leigh M. Stevens ◽  
...  
Keyword(s):  
Land Use ◽  
New Zealand ◽  
Physical Properties ◽  
Nutrient Loading ◽  
Management Strategies ◽  
Nutrient Concentrations ◽  
Intertidal Area ◽  
Land Use Patterns ◽  
Regional Patterns ◽  
Nitrogen Concentrations

Abstract We developed a method to predict the susceptibility of New Zealand estuaries to eutrophication. This method predicts macroalgae and phytoplankton responses to potential nutrient concentrations and flushing times, obtained nationally from simple dilution models, a GIS land-use model and physical estuary properties. Macroalgal response was based on an empirically derived relationship between potential nitrogen concentrations and an established macroalgal index (EQR) and phytoplankton response using an analytical growth model. Intertidal area was used to determine which primary producer was likely to lead to eutrophic conditions within estuaries. We calculated the eutrophication susceptibility of 399 New Zealand estuaries and assigned them to susceptibility bands A (lowest expected impact) to D (highest expected impact). Twenty-seven percent of New Zealand estuaries have high or very high eutrophication susceptibilities (band C or D), mostly (63% of band C and D) due to macroalgae. The physical properties of estuaries strongly influence susceptibility to macroalgae or phytoplankton blooms, and estuaries with similar physical properties cluster spatially around New Zealand’s coasts. As a result, regional patterns in susceptibility are apparent due to a combination of estuary types and land use patterns. The few areas in New Zealand with consistently low estuary eutrophication susceptibilities are either undeveloped or have estuaries with short flushing times, low intertidal area and/or minimal tidal influx. Estuaries with conditions favourable for macroalgae are most at risk. Our approach provides estuary-integrated susceptibility scores likely to be of use as a regional or national screening tool to prioritise more in-depth estuary assessments, to evaluate likely responses to altered nutrient loading regimes and assist in developing management strategies for estuaries.

scholarly journals Seasonal dynamics of native and invasive Halophila stipulacea populations—A case study from the northern Gulf of Aqaba and the eastern Mediterranean Sea

2020 ◽  
Vol 162 ◽  
pp. 103205 ◽  
Author(s):  
Hung Manh Nguyen ◽  
Ioannis Savva ◽  
Periklis Kleitou ◽  
Demetris Kletou ◽  
Fernando P. Lima ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Seasonal Dynamics ◽  
Eastern Mediterranean ◽  
Gulf Of Aqaba ◽  
Eastern Mediterranean Sea ◽  
Halophila Stipulacea

Ethalfluralin Activity in Cucumber (Cucumis sativus)

Weed Science ◽  
1982 ◽  
Vol 30 (5) ◽  
pp. 498-502 ◽  
Author(s):  
Jeffrey F. Derr ◽  
Thomas J. Monaco
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Weed Control ◽  
Cucumis Sativus ◽  
Environmental Conditions ◽  
Heavy Rain ◽  
Field Studies ◽  
Herbicidal Activity ◽  
Fresh Weight ◽  
Fresh Market

In greenhouse studies, soil organic matter reduced the herbicidal activity of ethalfluralin (N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine). Fifty percent inhibition (I5.0) values for barnyardgrass [Echinochloa crus-galli(L.) Beauv.] stand, injury, and shoot fresh weight increased as the soil organic-matter level increased. No difference in ethalfluralin tolerance was found among 16 cucumber (Cucumis sativusL.) cultivars. When grouped according to market type, fresh market cultivars tended to be injured more than pickling cultivars by excess ethalfluralin. Both shoots and roots of cucumber absorbed the herbicide, but exposure of roots to ethalfluralin was more toxic than exposure of shoots. Field studies indicated that with certain edaphic and environmental conditions, cucumbers can be injured by preemergence applications of ethalfluralin. Injury was greatest in a low organic-matter soil following a heavy rain. Ethalfluralin at 1.3 kg/ha gave adequate weed control in 1 and 3% organic-matter soils, but not in a 9% organic-matter soil.

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