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Tag: pollution

Eutrophication: A powerful poison to aquatic life

Posted on by Xi Lan

 

3Such tragic pictures were taken in China telling stories of the low-income people who live on fisheries lost their fishes due to the algae bloom. However, this problem does not only present in China: according to reports, during 1972 to 1999 US commercial fisheries lost over 18 million dollars every year due to the poor water quality (National Science Foundation, 2000).

 

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How is it developed?

Under warm and excessive nutrient conditions (e.g., introduction of nitrogen and phosphorus), algae in the lake starts to grow rapidly. In most healthy lakes, all depths are well oxygenated and the species in lakes are diverse. The excessive nutrient loads leads to the dominance of algae to the lakes, in other word, algae bloom. Massive algae bloom in the surface results in water turbidity increasing therefore the sunlight is blocked from underwater plants. Additionally, algae in the lakes has a short lifespan and depletes the oxygen in water causing a death zone along the water column (hypoxia); some algae can release toxins which are deadly to fish (Hallegraeff, 1993). In this stage the amount of fishes along with aquatic plants decreases rapidly. The healthy, well-oxygenated and clear lake becomes turbid, unsightly with few species alive and a disgusting smell.

 

What happens to ecosystem within the lake?
1The submerged aquatic plants which are adapted themselves to original lake conditions (e.g. high concentration of chlorophyll) are almost wiped out from the lakebed during the algae bloom (Jupp and Spence, 1977). In the case of Taihu lake in China, the area covered by submerged aquatic plants was over 530 km2 which reduced to around 300 km2   in 2009 (Qin et al., 2012).

The decreasing amount aquatic plants would have an impact to the zooplanktons. Less coverage of submerged aquatic plants on lakebed means less refuge capacity provided for zooplanktons (SCHRIVER et al., 1995). Therefore, besides the pressure of hypoxia, zooplanktons are struggling to survive at high predation risk.

One pronounced impact of lake eutrophication is the decreasing trend of overall fish population along with rising algal population as oxygen depleted environment is no longer able to hold big fish population as a healthy lake. Aparting from decreasing quantity of fish community, the fish community quality is also under threat. Generally, highly eutrophic lakes often are dominated by ferocious fish species such as carp (Lee and Jones, 1991). They are more adapted to the poorly oxygenated environment and they are voracious predator of zooplanktons that eat algae, which is an enhancing factor of lake eutrophication (Reinertsen et al., 1990). Decreasing fish community diversity could also happen when low oxygen condition driving deep-water living fish coming to open water under oxygen pressure which result in hybrid with open water fish.

 

Human interference to the ecosystem

Under such environmental pressure, countries like China decides to apply biotic approach to solve the algae bloom causing by eutrophication. Deploying algae-munching fish is well-known as approach to regulate algae population (Andersson et al., 1978). However, massive releasing algae-munching fish would dramatically changing the composition of current aquatic community leading unpredictable problems in future.

 

 

 

References

Andersson, G., Berggren, H., Cronberg, G. and Gelin, C. (1978). Effects of planktivorous and benthivorous fish on organisms and water chemistry in eutrophic lakes. Hydrobiologia, 59(1), pp.9-15.

Hallegraeff, G. (1993). A review of harmful algal blooms and their apparent global increase*. Phycologia, 32(2), pp.79-99.

Jupp, B. and Spence, D. (1977). Limitations on Macrophytes in a Eutrophic Lake, Loch Leven: I. Effects of Phytoplankton. The Journal of Ecology, 65(1), p.175.

Lee, G. and Jones, A. (1991). Effects of Eutrophication on Fisheries. Reviews in Aquatic Science, [online] 5(3). Available at: http://www.gfredlee.com/Nutrients/Effects_Eutroph_Fisheries.pdf             [Accessed 22 Mar. 2017].

McKinnon, J. and Taylor, E. (2012). Biodiversity: Species choked and blended. Nature, 482(7385), pp.313-314.

National Science Foundation, (2000). Estimated Annual Economic Impacts from Harmful Algal Blooms (HABs) in the United States. [online] National Science Foundation. Available at:                       http://www.whoi.edu/cms/files/Economics_report_18564_23050.pdf [Accessed 22 Mar. 2017].

Qin, B., Gao, G., Zhu, G., Zhang, Y., Song, Y., Tang, X., Xu, H. and Deng, J. (2012). Lake eutrophication and its ecosystem response. Chinese Science Bulletin, 58(9), pp.961-970.

Reinertsen, H., Jensen, A., Koksvik, J., Langeland, A. and Olsen, Y. (1990). Effects of Fish Removal on the Limnetic Ecosystem of a Eutrophic Lake. Canadian Journal of Fisheries and Aquatic             Sciences, 47(1), pp.166-173.

SCHRIVER, P., BOGESTRAND, J., JEPPESEN, E. and SoNDERGAARD, M. (1995). Impact of submerged macrophytes on fish-zooplanl phytoplankton interactions: large-scale enclosure                         experiments in a shallow eutrophic lake. Freshwater Biology, 33(2), pp.255-270.

 

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Diamonds aren’t Forever, as Villainous Tourists have a ‘License to Kill’ the World’s Coral Reefs

Posted on by Thomas Manktelow

Tourism is killing coastlines worldwide, destroying crucial coral reefs and the immense diversity within these ecosystems. Humans are irreversibly changing the marine environment!

There is a modern urge to travel the world; tropical, coastal areas increasingly visited for the sun and climate. More money in these regions puts natural systems at-risk, increased development and uncontrolled tourism affecting ecosystems such as coral reefs. Tourism has the ability to severely degrade coral reefs, introduced below (4earthTV, 2016).


Akumal Case Study

Akumal, Mexico, is an example of a coastline and reef ravaged by tourism. The number of hotel rooms in the region has increased by 80,000 in the last 30 years (Gil et al, 2015).
I have seen for myself the extent of the local environment change, which has had obvious negative effects on the health of the Mesoamerican barrier reef (BBC Earth, 2014).

In Akumal’s popular snorkeling areas, coral cover declined by 79% between 2011 and 2014. Globally, holiday activities have negative effects on the coral and on the native reef species (Gil et al, 2015). Turtle and shark populations suffer increased stress as tourism and tourists dominate the coastline (Constantine, 2001). Coral reefs are very sensitive to rapid tourism development, the popularity of these areas increasing algal cover and coral disease in the community (Garpow, 1999).

Tourism and boat traffic in Akumal Bay, Akumal (Photo: J. Houston)
Tourism and boat traffic in Akumal Bay, Akumal (Photo: J. Houston)

Hotel Pollution

Another consequence of global change are the septic tanks from growing hotel complexes, which feed coral reefs with nutrients, boosting the growth of algae and negatively changing the system. This clouds the water, meaning sunlight cannot reach the coral, causing unhealthy reef conditions (Garpow, 1999). Tourists are a huge environmental change impacting coral reefs. Coastal resorts attract the greatest number of tourists annually, often because of our growing desire to view coral reefs (Davenport & Davenport, 2006).

 

SCUBA Divers and Snorkelling

Worldwide, SCUBA divers and swimmers can severely damage the reef – in crowded areas, coral contact can lead to 100% mortality (Reef Resilience, 2016), inflicting abrasion and tissue loss (Davenport & Davenport, 2006). Tourists can also suffocate the coral, stirring up silt and encouraging algal domination. Coral reefs are also experiencing more boat traffic, which can disrupt coral communities, upsetting species interactions. Using boat anchors on the reef can damage the coral for decades, lowering reproductive health and species fitness (Rogers and Garrison, 2001).

Left: Snorkeler touching native turtle (Photo: J.Bartoszec, 2010). Right: Brain coral suffering anchor damage (Photo: Z. Livnat)
Left: Snorkeler touching native turtle (Photo: J.Bartoszec, 2010). Right: Brain coral suffering anchor damage (Photo: Z. Livnat)


The Future of Coral Reefs

There are global plans to increase tourism around coral reefs, building additional hotels. Human pollution will increase; sun-cream and E. coli contamination expected to impact reef health. Marine turtles are also developing tumours from a tourism-borne virus, demonstrating the reduced health of coral reefs and the species within them; all because of tourism (Sanchez-Navarro Russell, 2016).

Coral reefs across the world are experiencing problems associated with tourism. Fifty years ago reefs were untouched; only in the last 30 years have coral reefs become a primary tourist attraction. The coastline has changed so dramatically that slow-growing coral and the species within them cannot adapt fast enough and are suffering greatly.

Tourism has the potential to kill existing coral reefs; therefore, it is our responsibility to manage coastlines with greater effect, and as tourists, show greater respect towards the marine environment.

 

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References

BBC Earth. (2014). The Struggle to Save the Caribbean’s Huge Barrier Reef. Available: http://www.bbc.co.uk/earth/story/20141128-the-other-great-barrier-reef. Last accessed 13th March 2017

Constantine (2001), Increased Avoidance of Swimmers by Bottlenose Dolphins (Tursiops truncatus) due to Long-Term Exposure to Swim-With-Dolphin Tourism, Marine Mammal Science. 17 (4), p689-702.

Davenport and Davenport (2006), Impact of Tourism and Personal Leisure Transport on Coastal Environments: A Review. Estuarine, Coastal and Shelf Science. 67, p280-292.

Garpow, W (1999), Sustainability Indicators Regarding Tourism Development and Coral Reef Conservation: A Case Study of Akumal in the Caribbean, Proceedings of the 1999 Northeastern Recreation Research Symposium. P23-29.

Gil et al (2015), Rapid Tourism Growth and Declining Coral Reefs in Akumal Mexico, Marine Biology. 162 (11), p2225-2233

Reef Resilience (2016), Tourism and Recreational Impacts. Available: http://www.reefresilience.org/coral-reefs/stressors/local-stressors/coral-reefs-tourism-and-recreational-impacts/. Last accessed 13th March 2017.

Rogers and Garrison (2001), Ten Years after the Crime: Lasting Effects of Damage from a Cruise Ship Anchor on a Coral Reef in St. John, U.S. Virgin Islands. Bulletin of Marine Science. 69 (2), p793-803.

Sanchez-Navarro Russell (2016), Akumal Suffering from Unsustainable Growth. Available: http://mexiconewsdaily.com/opinion/akumal-suffering-from-unsustainable-growth/. Last accessed 13th March 2017.

4earthTV. (2016). Coral Reef Conservation: 4earthTV. Available: https://www.youtube.com/watch?v=OGcnzggMqKA. Last accessed 22nd March 2017.



Are plants on their way to killing us?

Posted on by Charlotte Alanine

          Have you ever noticed how much easier it is to breathe on a jog through a luscious park or a woodland compared to the inner city? This is because the air we breathe comes from the photosynthetic process plants provide. In this reaction, plants extract energy from carbon dioxide (CO2) combined with sunlight as well as other organic soil materials and release Oxygen (O2) as a by-product which we then benefit from.

 

         Photosynthesis under increasing CO2

          Each year since 1959, approximately half of the CO2 emissions we produce linger in our atmosphere (Le Quéré, et al., 2009). With atmospheric levels of CO2 on the rise as a result of our activities, the logical outcome would be that plants have additional CO2 to photosynthesise, allowing for more oxygen for us, right? Indeed, short-term increases have no negative impacts on photosynthesis. In fact, a study suggested they became more efficient at recycling CO2 (Besford, et al., 1990) as demonstrated in the positive feedback photosynthesis and growth of P.cathayana (Zhao, et al., 2012). However, under long-term carbon dioxide exposure, plants lost all photosynthetic gain (Besford, et al., 1990). Other studies have investigated the effects of increasing CO2 levels on plants and it has recently been found that previous models may have overestimated  the ability of plant “sinks” to make use of the additional human-related carbon. A “sink” is a location where carbon dioxide accumulates and is absorbed by plants much like running water down a sink.

 

From carbon sinks to carbon sources

        In 1991, Arp projected that plants in the field would not experience a decrease in photosynthetic abilities as a result of atmospheric CO2 increase. However, more recently in 2015, Wieder et al. reported that photosynthetic processes were limited by nutrient availability, in which phosphorus and nitrogen (Aranjuelo, et al., 2013) were the main limiting factors.

Figure 1. Modelling of changes in mean terrestrial carbon storage from an initial record 1860-1869 (top) to the 2100 projection with limited nitrogen and phosphorus (bottom). Source: Wieder et al. (2015)
Figure 1. Modelling of changes in mean terrestrial carbon storage from an initial record 1860-1869 (top) to the 2100 projection with limited nitrogen and phosphorus (bottom). Source: Wieder et al. (2015)

          In addition, their models projected that by 2100, plants which were once considered sinks may actually be turning into carbon sources (fig.1). This means they could be emitting more carbon than they absorb as a result of increasing carbon dioxide in the air in combination with the insufficient amounts of other organic materials (nitrogen, phosphorus, minerals, etc.) necessary for photosynthesis and consequently accelerating the rate of climate change which is bad news for us. Plants will essentially be slowly suffocating us as we rely on them for clean air.

 

 

 

A threat to food security

          Likewise, as a result of intensifying agriculture, soils are becoming increasingly eroded. For one, this means they are unable to store and process atmospheric carbon as efficiently and there is a lack of nutrients made available to plants (Lal, et al., 2008). This, coupled with the higher concentrations of CO2, poses a great threat to major crop plants such as oilseed rape (Franzaring, et al., 2011) and wheat (Uddling, et al., 2008). In laboratory studies, these crop plants tended to reduce the quality and quantity of their seeds in high concentrations of CO2.

          Emissions are not only posing a threat to a plant’s capacity to recycle air but also put our food security at risk.

References

Aranjuelo, I., Cabrerizo, P., Arrese-Igor, C. & Aparicio-Tejo, P., 2013. Pea plant responsiveness under elevated [CO2] is conditioned by the N source (N2 fixation versus NO3 – fertilization). Environmental and Experimental Botany, Volume 95, pp. 34-40.

Arp, W., 1991. Effects of source-sink relations on photosynthetic acclimation to elevated CO2. Plant, Cell and Environment, Volume 14, pp. 869-875.

Besford, R., Ludwig, L. & Withers, A., 1990. The Greenhouse Effect: Acclimation of Tomato Plants Growing in High CO2, Photosynthesis and Ribulose-1, 5-Bisphosphate Carboxylase Protein. Journal of Experimental Botany, 41(8), pp. 925-931.

Franzaring, J., Weller, S., Schmid, I. & Fangmeier, A., 2011. Growth, senescence and water use efficiency of spring oilseed rape (Brassica napus L. cv.Mozart) grown in a factorial combination of nitrogen supply and elevated CO2. Environmental and Experimental Botany, Volume 72, pp. 284-296.

Lal, R. et al., 2008. Soil erosion: a carbon sink or source?. Science, 319(5866), pp. 1040-1042.

Le Quéré, C. et al., 2009. Trends in the sources and sinks of carbon dioxide. Nature geoscience, 2(12), pp. 831-836.

Uddling, J. et al., 2008. Source-sink balance of wheat determines responsiveness of grain production to increased [CO2] and water supply. Agriculture, Ecosystems and Environment, Volume 127, pp. 215-222.

Wieder, W., Cleveland, C., Smith, W. & Todd-Brown, K., 2015. Future productivity and carbon storage limited by terrestrial nutrient availability. Nature, 8(6), pp. 441-445.

Zhao, H. et al., 2012. Sex-related and stage-dependent source-to-sink transition in Populus cathayana grown at elevated CO2 and elevated temperature. Tree Physiology, Volume 32, pp. 1325-1338.

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