The University of Southampton

Tag: Sea level rise

Humanity must stop neglecting changes in Seagrass Meadows before disaster?

Posted on by Anonymous

Seagrass meadows are a vital habitat and food source for many endangered species but these crucial habitats are under threat from environmental change caused by human impacts climate change, coastal developments, fishing and aquaculture (Waycott etal, 2009).

Figure 1- Manatee feeding on seagrass (USGS, 2016)
Figure 1- Manatee feeding on seagrass (USGS, 2016)

Climate Change

Climate change will cause a wide variety of impacts on the oceans which will effect seagrasses increasing water temperatures will lead to increased instances of seagrass die off, ocean acidification caused damaged to the cells plants require to photosynthesize and grow (Repolho et al, 2017).

As seagrass requires shallow habitats as sea levels rise there will be a loss of seagrass in deeper areas of their range seagrasses will move shoreward this trend is similar to trends that are being seen from increased amounts of sediments within the water as they will lack the sunlight to photsynthesise (Davis et al, 2016).

Coastal Developments

The construction of ports, artificial beaches and the reclamation of land, the adding of material to the water to fill in the area, this leads to more sediments within the water. The increased amount of sediments in the water can lead to seagrass beds being completely buried by the sediment and stopping plants from photosynthesising which it needs to survive, during the construction of the Pointe-Rouge Harbour over 68ha of seagrasses were lost due to water sediment and 11ha destroyed by construction (Boudouresque et al, 2009).

Figure 2- The Light grey shows dead seagrass and the dark grey living seagrass after the laying of a cable between two islands in the South of France (Boudouresque et al, 2009)
Figure 2- The Light grey shows dead seagrass and the dark grey living seagrass after the laying of a cable between two islands in the South of France (Boudouresque et al, 2009)

 

Fishing and Aquaculture

A trawler can uproot between 99,000-363,000 shoots during a trawl and in some areas of the Mediterranean over 80% of the seagrass meadows have been destroyed due to trawling (Boudouresque et al, 2009). Aquaculture, mainly fish farms, can cause a process called eutrophication, an excessive increase in nutrients heading into a body of water leading to high algal growth, because of the nutrients from uneaten food and excretion from the fish as it is focussed in one area around the fish farm this causes the reduction in size of the plants in the area due to reduced light reaching the plants, leading to a regression of the plants in the areas around fish farms (Ruiz et al, 2001).

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Figure 3- Changes in seagrass area by coastlines and in most coastlines more studies report a decrease (Waycott et al, 2009).

Future of Endangered Species

Dugongs, sea turtles and manatees all directly depend upon seagrass in many tropical regions for food and with decreases in seagrass globally, figure 3, they is likely to be further pressure put onto these already endangered species (Waycott et al, 2009), and if humanity does not take steps to solving the problems mentioned here the future of these iconic species is in real danger.

 

 

Reference List

Boudouresque, C., Bernard, G., Pergent, G., Shili, A., Verlaque, M., (2009), Regression of Mediterranean seagrasses caused by natural processes and anthropogenic disturbances and stress: a critical review, Botanica Marina, 52, 395-418

Davis, T., Harasti, D., Smith, S., Kelaher., (2016), Using modelling to predict impacts of sea level rise and increased turbidity on seagrass distributions in estuarine embayments, Estuarine, Coastal and Shelf Science, 181, 294-301

Repolho, T., Duarte, B., Dionísio, G., Paula, J., Lopes, A., Rosa, I., Grilo, T., Caçador, I., Calado, R. and Rosa, R. (2017). Seagrass ecophysiological performance under ocean warming and acidification. Scientific Reports, 7, p.41443.

Ruiz, J., Perez, M., Romero, J., (2001), Effects of Fish Farm Loadings on Seagrass (Posidonia oceanica) Distribution, Growth and Photosynthesis, Marine pollution bulletin, 42(9), 749-760

USGS, (2016). Manatees [online] Available at: https://www.usgs.gov/centers/wetland-and-aquatic-research-center-warc/science-topics/manatees [Accessed 20 Mar. 2017].

Waycott, M., Duarte, C., Carruthers, T., Orth, R., Dennison, W., Olyarnik, S., Calladine, A., Fourqurean, J., Heck, K., Hughes, A., Kendrick, G., Kenworthy, W., Short, F. and Williams, S., (2009). Accelerating loss of sea grass across the globe threatens coastal ecosystems,. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(30), 12377-12381

 

Word Count – 489

 

 

 



The tide is high but I’m holding on: The effect of rising sea level on wetlands

Posted on by Sophie Gibson

Sea levels have been rising over the years due to water expansion and glaciers melting (Jacob et al, 2012). Unfortunately unlike Blondie not all of our coastal systems can ‘hold on’ and survive this. There have been effects on wetlands (Scavia, 2002) such as marshes and mangroves by:

  • Inundation (flooding)
  • Salt water intrusion
  • Erosion

 

Marshes 

A flooded marsh being broken up due to flooding. Image from: http://www.learnnc.org/lp/editions/cede_sealevel/373
A salt marsh being broken up due to flooding. Image from: www.learnnc.org

Rising sea levels increase the frequency and duration of tidal flooding in marshes (Titus, 1988). If these marshes are supplied with additional sediment then they can retreat landwards and keep up with sea level rise.  However if they aren’t Usain Bolt enough to outrun sea level, the marsh grass drowns, soil erodes and the system is lost and often becomes open water. This usually occurs in salt water coastal marshes (Scavia et al, 2002).                                                                                  

Another effect of rising sea level allows salt water to move upstream and inland to the freshwater marshes, causing them to transition into a brackish (slightly salty) marsh. Often, a response is to replace freshwater species with more salt tolerant species, therefore changing the biodiversity and functioning of the system.

Marshes are very important as nursery grounds, giving protection to marine invertebrates and fish larvae and are also an important food source for aquatic birds such as sandpipers as well as other large animals (Titus, 1988). They are also vastly important for humans as they provide services associated with waste treatment and productivity. These processes will likely be affected with the reduction of salt marshes and the transition of fresh water marshes to brackish (Craft et al, 2009).

 

Video summarising the effects of sea level rise on marshes. 

Mangroves 

Mangrove roots supporting biodiversity. Image from: http://www.bbc.co.uk/nature/habitats/Mangrove
Mangrove roots supporting biodiversity.                 Image from: www.bbc.co.uk

Mangroves adjust to a rising sea level by moving into areas of higher elevation. This movement however can be limited by obstacles, steep gradients and the amount of sediment accumulation (Gilman et al, 2008). Different species have different colonisation speeds, leading to competition between species. This can cause some to become more dominant than others, affecting biodiversity. (Di Nitto et al, 2014). 

Mangroves can’t always move faster than sea level rise and the increased flooding can cause roots to weaken, trees to die and the system to become open water. Even when they are able to move, many mangroves are losing elevation relative to sea level (Gilman et al, 2008) (Lovelock et al, 2015).

 Mangroves are important:

  • For supporting biodiversity
  • As fishery nursery habitats
  • For coastal protection 
  • For carbon uptake

 

and are therefore relied on by many human communities (Di Nitto et al, 2014). These effects are likely to get worse in the coming years and therefore more research should be carried out and protection plans put in place. 

Scale model showing how mangrove forests protect the coast from wave erosion.

Overall wetlands are thought to be most affected on the Atlantic Coast of Central and North America, Caribbean islands, the Mediterranean and Baltic (Nicholls, Hoozemans And Marchand, 1999). So remember, wetlands aren’t just some soggy plants! They are vital ecosystems that have important functions and their loss could cause many issues especially in the coming years as sea level continues to rise. 

References 

Craft, C., Clough, J., Ehman, J., Joye, S., Park, R., Pennings, S., Guo, H. and Machmuller, M. (2009). Forecasting the effects of accelerated sea-level rise on tidal marsh ecosystem services. Frontiers in Ecology and the Environment, 7(2), pp.73-78.

Di Nitto, D., Neukermans, G., Koedam, N., Defever, H., Pattyn, F., Kairo, J. and Dahdouh-Guebas, F. (2014). Mangroves facing climate change: landward migration potential in response to projected scenarios of sea level rise. Biogeosciences, 11(3), pp.857-871.

Gilman, E., Ellison, J., Duke, N. and Field, C. (2008). Threats to mangroves from climate change and adaptation options: A review. Aquatic Botany, 89(2), pp.237-250.

Jacob, T., Wahr, J., Pfeffer, W. and Swenson, S. (2012). Recent contributions of glaciers and ice caps to sea level rise. Nature, 482(7386), pp.514-518.

Lovelock, C., Cahoon, D., Friess, D., Guntenspergen, G., Krauss, K., Reef, R., Rogers, K., Saunders, M., Sidik, F., Swales, A., Saintilan, N., Thuyen, L. and Triet, T. (2015). The vulnerability of Indo-Pacific mangrove forests to sea-level rise. Nature, 526(7574), pp.559-563.

Nicholls, R., Hoozemans, F. and Marchand, M. (1999). Increasing flood risk and wetland losses due to global sea-level rise: regional and global analyses. Global Environmental Change, 9, pp.S69-S87.

Scavia, D., Field, J., Boesch, D., Buddemeier, R., Burkett, V., Cayan, D., Fogarty, M., Harwell, M., Howarth, R., Mason, C., Reed, D., Royer, T., Sallenger, A. and Titus, J. (2002). Climate change impacts on U.S. Coastal and Marine Ecosystems. Estuaries, 25(2), pp.149-164.

Titus, J. (1988) Sea Level Rise and Wetland Loss: An Overview U.S Environmental Protection Agency.

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