Predation by the black-clawed mud crab,Panopeus herbstii, in Mid-Atlantic salt marshes: Further evidence for top-down control of marsh grass production

Wetland restoration provides remarkable opportunities to understand vegetation dynamics and to inform success of future projects through rigorous restoration experiments. Salt marsh restoration typically focuses on physical factors such as sediment dynamics and elevation. Despite many demonstrations of strong top-down effects on salt marshes, the potential for consumers to affect salt marsh restoration projects has rarely been quantified. Recently, major restoration projects at the Elkhorn Slough National Estuarine Research Reserve in central California, USA provided an opportunity to examine how herbivory influences restoration success. We quantified the strength of consumer effects by comparing caged to uncaged plantings, and compared effects among plant species and sites. We used camera traps to detect which herbivores were most common and how their abundance varied spatially. Beyond characterizing consumer effects, we also tested management strategies for reducing negative effects of herbivory at the restoration sites, including caging, mowing, and acoustic playbacks of predator sounds. We found extremely strong consumer effects at sites with extensive stands of exotic forbs upland of the high marsh; uncaged restoration plants suffered heavy herbivory and high mortality, while most caged plants survived. Brush rabbits (Sylvilagus bachmani) were by far the most frequent consumers of these high marsh plants. Our work thus provides the first evidence of mammal consumers affecting salt marsh restoration success. Mowing of tall exotic forb cover adjacent to the marsh at one restoration site greatly reduced consumption, and nearly all monitored plantings survived at a second restoration site where construction had temporarily eliminated upland cover. Playbacks of predator sounds did not significantly affect restoration plantings, but restoration efforts in marsh communities vulnerable to terrestrial herbivory may benefit from concurrent restoration of predator communities in the upland habitats surrounding the marsh. A landscape approach is thus critical for recognizing linkages between terrestrial and marine vegetation.

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Identifying critical transitions in seasonal shifts of zooplankton composition in a confined coastal salt marsh

Aquatic Sciences ◽

10.1007/s00027-021-00824-5 ◽

2021 ◽

Vol 83 (4) ◽

Author(s):

Xavier D. Quintana ◽

Maria Antón-Pardo ◽

Maria Bas-Silvestre ◽

Dani Boix ◽

Xavier Casamitjana ◽

...

Keyword(s):

Salt Marshes ◽

Dominant Species ◽

Resistance To Change ◽

Alternative Stable States ◽

Zooplankton Biomass ◽

The Other ◽

Stable States ◽

Top Down ◽

Bottom Up ◽

Critical Transitions

AbstractZooplankton assemblages in the confined coastal lagoons of La Pletera salt marshes (Baix Ter wetlands, Girona, Spain) are dominated by two species: one calanoid copepod (Eurytemora velox) and the other rotifer (Brachionus gr. plicatilis). They alternate as the dominant species (more than 80% of total zooplankton biomass), with the former being dominant in winter and the latter in summer. Shifts between these taxa are sudden, and intermediate situations usually do not last more than 1 month. Although seasonal shifts between zooplankton dominant species appear to be related with temperature, other factors such as trophic state or oxygen concentration may also play an important role. Shifts between species dominances may be driven by thresholds in these environmental variables. However, according to the alternative stable states theory, under conditions of stable dominance a certain resistance to change may exist, causing that gradual changes might have little effect until a tipping point is reached, at which the reverse change becomes much more difficult. We investigated which are the possible factors causing seasonal zooplankton shifts. We used high-frequency temperature and oxygen data provided by sensors installed in situ to analyse if shifts in zooplankton composition are determined by a threshold in these variables or, on the other hand, some gradual change between stable states occur. Moreover, following the postulates of the alternative stable states theory, we looked at possible hysteresis to analyse if these seasonal zooplankton shifts behave as critical transitions between two different equilibriums. We also examined if top-down or bottom-up trophic interactions affect these zooplankton shifts. Our results show that shifts between dominant zooplankton species in La Pletera salt marshes are asymmetric. The shift to a Eurytemora situation is mainly driven by a decrease in temperature, with a threshold close to 19 °C of daily average temperature, while the shift to Brachionus does not. Usually, the decrease in water temperature is accompanied by a decrease in oxygen oscillation with values always close to 100% oxygen saturation. Moreover, oxygen and temperature values before the shift to calanoids are different from those before the reverse shift to Brachionus, suggesting hysteresis and some resistance to change when a critical transition is approaching. Top-down and bottom-up forces appear to have no significant effect on shifts, since zooplankton biomass was not negatively correlated with fish biomass and was not positively related with chlorophyll, in overall data or within shifts.

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Major role of marine vegetation on the oceanic carbon cycle

Biogeosciences ◽

10.5194/bg-2-1-2005 ◽

2005 ◽

Vol 2 (1) ◽

pp. 1-8 ◽

Cited By ~ 594

Author(s):

C. M. Duarte ◽

J. J. Middelburg ◽

N. Caraco

Keyword(s):

Organic Carbon ◽

Salt Marshes ◽

Total Carbon ◽

Organic Carbon Content ◽

Top Down ◽

Coastal Habitats ◽

Bottom Up ◽

Seagrass Meadows ◽

Carbon Burial ◽

Oceanic Carbon

Abstract. The carbon burial in vegetated sediments, ignored in past assessments of carbon burial in the ocean, was evaluated using a bottom-up approach derived from upscaling a compilation of published individual estimates of carbon burial in vegetated habitats (seagrass meadows, salt marshes and mangrove forests) to the global level and a top-down approach derived from considerations of global sediment balance and a compilation of the organic carbon content of vegeatated sediments. Up-scaling of individual burial estimates values yielded a total carbon burial in vegetated habitats of 111 Tmol C y-1. The total burial in unvegetated sediments was estimated to be 126 Tg C y-1, resulting in a bottom-up estimate of total burial in the ocean of about 244 Tg C y-1, two-fold higher than estimates of oceanic carbon burial that presently enter global carbon budgets. The organic carbon concentrations in vegetated marine sediments exceeds by 2 to 10-fold those in shelf/deltaic sediments. Top-down recalculation of ocean sediment budgets to account for these, previously neglected, organic-rich sediments, yields a top-down carbon burial estimate of 216 Tg C y-1, with vegetated coastal habitats contributing about 50%. Even though vegetated carbon burial contributes about half of the total carbon burial in the ocean, burial represents a small fraction of the net production of these ecosystems, estimated at about 3388 Tg C y-1, suggesting that bulk of the benthic net ecosystem production must support excess respiration in other compartments, such as unvegetated sediments and the coastal pelagic compartment. The total excess organic carbon available to be exported to the ocean is estimated at between 1126 to 3534 Tg C y-1, the bulk of which must be respired in the open ocean. Widespread loss of vegetated coastal habitats must have reduced carbon burial in the ocean by about 30 Tg C y-1, identifying the destruction of these ecosystems as an important loss of CO2 sink capacity in the biosphere.

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Polarized light sensitivity in the stage I zoea of the mud crab Panopeus herbstii

Marine Biology ◽

10.1007/bf00391404 ◽

1978 ◽

Vol 46 (4) ◽

pp. 327-333 ◽

Cited By ~ 5

Author(s):

M. Bardolph ◽

R. H. Stavn

Keyword(s):

Polarized Light ◽

Light Sensitivity ◽

Stage I ◽

Mud Crab ◽

Panopeus Herbstii

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REMOVING OIL AND SAVING OILED MARSH GRASS USING A SHORELINE CLEANER

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1995-1-203 ◽

1995 ◽

Vol 1995 (1) ◽

pp. 203-209 ◽

Cited By ~ 5

Author(s):

S. R. Pezeshki ◽

R. D. DeLaune ◽

J. A. Nyman ◽

R. R. Lessard ◽

G. P. Canevari

Keyword(s):

Spartina Alterniflora ◽

Salt Marshes ◽

Gulf Coast ◽

Control Plant ◽

Soil Microbial Communities ◽

Soil Microbial ◽

Plant Photosynthesis ◽

Greenhouse Plant ◽

And Control ◽

Marsh Grass

ABSTRACT A new shoreline cleaner, which was specially developed during the cleanup of the Valdez spill in Alaska, was tested to determine its effectiveness in removing oil from Louisiana Gulf Coast marsh grass thus minimizing the oil impact. Intact plugs of Spartina alterniflora containing living plants, roots, and soil microbial communities were collected from salt marshes and transferred to a greenhouse. Plant photosynthesis, respiration, and stomatal conductance were monitored following various oiling and cleaning scenarios. The treatments included: oiled, oiled and cleaned after one day, oiled and cleaned after two days, cleaner only, and control. Plant recovery depended upon the degree of oiling and the type of oil used. Fouling with bunker C oil caused almost total plant mortality unless the plants were cleaned with the shoreline cleaner. South Louisiana crude oil was less toxic but cleaning accelerated recovery as was evident by photosynthetic activity and other plant functions such as regeneration of new shoots. Collectively, these studies demonstrate the potential for saving an oiled Spartina alterniflora marsh by use of this shoreline cleaner in a real oil spill.

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