Experimental assessment of critical anthropogenic sediment burial in eelgrass Zostera marina

Abstract

Seagrass meadows, one of the world's most important and productive coastal habitats, are threatened by a range of anthropogenic actions. Burial of seagrass plants due to coastal activities is one important anthropogenic pressure leading to the decline of local populations. In our study, we assessed the response of eelgrass Zostera marina to sediment burial from physiological, morphological, and population parameters. In a full factorial field experiment, burial level (5-20cm) and burial duration (4-16weeks) were manipulated. Negative effects were visible even at the lowest burial level (5cm) and shortest duration (4weeks), with increasing effects over time and burial level. Buried seagrasses showed higher shoot mortality, delayed growth and flowering and lower carbohydrate storage. The observed effects will likely have an impact on next year's survival of buried plants. Our results have implications for the management of this important coastal plant.

Burial Duration and Frequency Influences Resilience of Differing Propagule Types in a Subtidal Seagrass, Posidonia australis

“…Many available sites for restoration efforts are in exposed and typically high sediment load, and therefore accreting, environments (e.g., [ 35 , 44 – 45 ]); concomitantly, seagrasses create an accreting ecosystem (e.g., [ 46 ]). Therefore, the rate and duration of burial is potentially a significant determinant of restoration success, particularly if the resilience to burial varies between species or transplant unit types (e.g., [ 14 , 28 , 47 ]). This study found that resilience to burial duration for Posidonia australis varied between transplant unit types.…”

“…Successful transplantation and restoration (or rehabilitation) of seagrass rely upon knowledge of the target species’ autecological requirements to determine the appropriate transplant unit type [ 5 , 6 ] and appropriate recipient site [ 5 ], including understanding if site specific stressors that led to seagrass decline have been ameliorated or removed. Equally important is the knowledge of how the species responds to disturbance events such as sediment burial, intensity of herbivory, and changing nutrient levels (e.g., [ 7 – 14 ]). Consequently, restoration and rehabilitation success may be heavily influenced by disturbance at a proposed transplant site.…”

“…Studies have illustrated that burial triggers photomorphogenic responses in seagrasses that result in the relocation of the meristem to the surface (where possible; e.g., [ 20 – 21 ]). Typically, seagrass burial studies have examined depth of burial as the determinant of disturbance (e.g., [ 8 , 11 , 22 – 27 ]) but few have focussed on the duration or frequency of burial (except see [ 14 , 28 ]) or examined the resilience to burial between propagule types. These few studies have suggested that pulse versus press burial events may produce differing outcomes for seagrass resilience [ 11 , 29 – 30 ].…”

“…These few studies have suggested that pulse versus press burial events may produce differing outcomes for seagrass resilience [ 11 , 29 – 30 ]. For example, press burial events can cause seagrass declines (e.g., [ 31 , 32 ]) and, contrary to ecological theory that pulse events would result in temporary effects, there is empirical evidence that some seagrasses are more likely to succumb to rapid pulse burial events [ 11 , 14 ] and persist or thrive in press burial events [ 28 , 29 ]. How seagrasses respond to pulse vs. press burial events remains largely unexplored, yet is critically needed to help select an appropriate seagrass transplant site and propagule type.…”

A low cost field‐survey method for mapping seagrasses and their potential threats: an example from the northern Gulf of Aqaba, Red Sea

“…Living under threat for at least a century, seagrasses may be nearing a crisis in terms of their global sustainability (Orth et al , ; Waycott et al , ). Reductions in water quality (Munkes et al , ), higher water temperatures (Greve et al , ; Reusch et al , ) and climate variability (e.g. summer heat waves; Ehlers et al , ; Bergmann et al , ; Winters et al , ) have all been identified as major threats to seagrass meadows (reviewed by Orth et al , ; Björk et al , ; Waycott et al , ).…”