What are the factors that can affect seagrass growth/ cause seagrass loss?
How does the changing environment impact the seagrass?
Based on notes from Dr Len McKenzie’s Seagrass Workshop last year, here’s a general list of factors that can affect the growth of seagrass!
Factors affecting Seagrass Growth
Current & Hydrodynamic (water movement) processes ·
Interactions with other species (e.g. there must be epiphytes to prevent the seagrass from “sunburn”, but too much epiphytes will suffocate the seagrass.)
(All this differs for different species types. )
*epiphyte: according to “http://en.wikipedia.org/wiki/Epiphyte”, ‘An epiphyte is an organism that grows upon or attached to a living plant.’ In this case, the living plant would be the seagrass.
Also based on the Seagrass Workshop conducted last year, here’s a list of the factors contributing to seagrass loss
Causes for seagrass loss (due to environment/machinery) to seagrass meadows
- dredging: removes plants and reduces light availability
- grazing (by turtles and dugongs): removes plants
- bait & clam digging: physical disturbances of plants, removes plants
- anchors & propellers: physical disturbances of plants (cuts up rhizomes, during storms, whole meadows can get uprooted)
- flooding: lots of deepwater/freshwater input, sedimentation, herbicide input
- increased sedimentation can lead to topography changes such as a raised seabed: overexposure to sunlight
- loss of shelter : loss of protection from wind/wave action
- Diseases: e.g. labyrinthula – slime mould·
- Elevated nutrients: too much epiphytes can smother leaves
- Poor catchment practices (diffuse & chronic inputs from modified catchment): sedimentation, herbicides
- Aquaculture: can result in increased algae blooms, increased sedimentation (block sunlight)
- Coastal land development: runoff, acid sulphate soils (sulphuric acid, washed out to seagrass meadow, kills animals), sedimentation
- Industrial ports: physical damage (ports often in protected areas, seagrass as well, they have to co-exist), change in topography and water flow, point source discharge (oil spills, sewage and industrial discharge)
- Shipping: physical damage from grounding, point source discharge
- Trawling: physical damage from intensive trawling
- Fishing: poisoning, blasting (high in phosphites, algae blooms), set nets (when they drag the nets to catch fish, they uproot sea grass)
- Physical damage by ignorant children/ adults
Finally, here’s a list of the impacts of climate change on seagrass.
Impacts of climate change on seagrass
increase in temperature: burnoff, affects distribution and reproduction
sea level rise, increasing water depth so exposure to light is reduced
disturbances through increased number and intensity of hurricanes/cyclones·
elevated flooding frequency and amplitude
slight rise in temperature (1-2 degrees Celcius) even for short period breaks down the enzymes needed for photosynthesis.