Tuesday, 28 October 2014

Red tide

  1. Red algal bloom at Leigh near Cape Rdney

    Red tide, also known as harmful algal blooms (HAB), is caused by algal blooms which discolour coastal water (Bruckner, 2014). Algal blooms usually arise due to excess nutrients released into water, encouraging rapid growth of algae. At the coast, favorable winds and waves push surface water offshore so deep water moves to the coast, bringing excess nutrients from the ocean to the surface (EPA, 2014). As a results, these excess nutrients promote abundant algae growth in such coastal areas. Red tide can spread to other area by wind, waves, storms and ships, which transport the algae related to the bloom elsewhere (Bruckner, 2014).

  2. A small percentage of algae produce toxins that can kill fish, shellfish, birds, mammals, and even humans (when consume poisoned shellfish or fish). Non-toxic algae can cause harm to marine wildlife. When large masses of algae die, decomposers take in oxygen to break down the dead matter, causing waters to become oxygen depleted and this leading to fish kills.
  3. References
  4. Bruckner, M. 2014. Red Tide - A Harmful Algal Bloom. [ONLINE] Available at:http://serc.carleton.edu/microbelife/topics/redtide/index.html. [Accessed 29 October 14].

    EPA. 2014. Climate Change and Harmful Algal Blooms. [ONLINE] Available at:http://www2.epa.gov/nutrientpollution/climate-change-and-harmful-algal-blooms. [Accessed 29 October 14].

    NOAA. 2014. Why do harmful algal blooms occur?. [ONLINE] Available at:http://oceanservice.noaa.gov/facts/why_habs.html. [Accessed 29 October 14].

Sunday, 26 October 2014

Invasive Species

The Lionfish which was previously unknown to America is now found  from Rhode Island to Belize.
An invasive species is one that exist in a habitat in which it does not belong. When a foreign species arrive at a new location, it can either find its new habitat unsuitable and die off or thrive and take over the habitat. The later occurs due to the lack of its predators to control its population.

Killer Algae (Caulerpa taxifolia):
The hybrid form of Caulerpa taxifolia came about due to the aquarium business. They wanted to find and bred a type of seaweed that can be used in commercially saltwater aquarium and have a attractive colour and form, making a nice backdrop for exotic fishes. However, after being exposed to chemicals and ultraviolet light for a long period of time, Caulerpa taxifolia became mutated. The species than leaked out into the environment when samples of it was transferred around. 

The hybrid seaweed is very strong and can survive in nutrients depleted areas, polluted water and in a wide range of temperature. As a result of being leaked into the environment, the species can cover the entire seabed. It produces toxins that is harmful to certain fishes and invertebrates and their eggs. Furthermore, there is hardly any marine organism that feed on it. The plant grows unrestrained and many marine organism leaves the area.  

 Zebra Mussel (Dreissena polymorpha):
The Zebra mussels were accidentally introduced by cargo ships in the North American Great Lakes from the Black Sea. Many marine species are stowed away in ship ballast and get released at the ships' destination. In the case of the Zebra mussels, it multiplied rapidly and staved out the Great Lake's native mussels species and got in the way of man made structures (e.g factory pipes and ships rudders). It has further spread to Canada and Mexico and a lot of money is spent annually to remove the species. 


Cotton, K.I. 2005. Introduced Species Summary Project: Killer Algae . [ONLINE] Available at:http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Caulerpa_taxifolia.htm. [Accessed 27 October 14]

Ocean portal. 2014. 5 Invasive Species You Should Know. [ONLINE] Available at:http://ocean.si.edu/ocean-news/5-invasive-species-you-should-know. [Accessed 27 October 14].

National geographic. 2014. Marine Invasive Species. [ONLINE] Available at:http://ocean.nationalgeographic.com/ocean/critical-issues-marine-invasive-species/. [Accessed 27 October 14]. 

Friday, 24 October 2014

Climate change and ocean acidification impacts on corals

Higher water temperature, brought about by increased carbon dioxide in atmosphere have adverse impact on coral reefs. Warmer temperature stress corals, causing zooxanthella to die or be expelled from the corals. This causes corals to lose their colour and turn white as the algae gives the coral its colour. Bleached corals are unhealthy and weak - less able to fight against diseases (Teachoceanscience, 2014).

Furthermore, as mentioned earlier posts, increase in carbon dioxide results to ocean acidification which leads to shells dissolving in the more acidic water. Likewise for corals, they are unable to absorb the calcium carbonate needed for their skeleton, and in the acidic water, the skeleton which supports coral reefs will dissolve.

Healthy corals

Unhealthy corals with their skeleton structure partially destroyed

Teachoceanscience.(2014) How does climate change affect coral reefs. [ONLINE] Available at:http://www.teachoceanscience.net/teaching_resources/education_modules/coral_reefs_and_climate_change/how_does_climate_change_affect_coral_reefs/. [Accessed 25 October 14].

Thursday, 23 October 2014

Ocean acidification: a shell game

Carbon dioxide from the atmosphere dissolve in the ocean water and combines with calcium to form calcium carbonated, which is needed to form shells. While some shelled marine organism increase their shell building, others partially dissolves in water with high carbon dioxide levels. In such waters, although there is more carbon available for shell formation, organism can only benefit if they can convert it into their shells and at the same time prevent their shells from dissolving in the more acidic water. Studies has found that different organism adapt differently in high carbon dioxide waters. While there is no observable change in shell building for large Caribbean snails, spines of pencil urchins dissolve to stumps in carbon rich waters. Other shell fishes' (oysters, clams and scallops) shell building rate decreases. 
The urchin on the left is gown in carbon dioxide water rich water whereas the the one on the right is gown in normal conditions (it is healthier with normal spines).
However, for certain crustaceans, it was tested that they grew heavier shells in carbon dioxide rich water. These species include American lobster, blue crab and a large prawn. 
American lobster grown in high carbon dioxide waters (right) grew larger and heavier shell as compared to those grown in normal conditions (left)
As a result, ocean acidification will cause some species to thrive and benefit over others. The main concern is for species that are unable to adapt well to the change in ocean's acidity.
 " Given the complex relationships that exist among benthic marine organisms", said Ries, " it is difficult to predict how even subtle changes in organisms' abilities to calcify will ultimately work their way through these ecosystems."
-Kate Madin

This blog post is based on the report 'Ocean acidification: a risky shell game'

WHOI, 2010. Ocean acidification: a risky shell game. Oceanus magazine, [Online]. 48 (1), 6-7. Available at: http://www.whoi.edu/cms/files/OceanAcid_68964.pdf [Accessed 23 October 2014].

Saturday, 18 October 2014

Ocean acidification

Carbon dioxide given off by vehicles, power plants and other human sources gas combines with seawater to form.

Ocean acidification, also known as "global warming's evil twin", it is a direct consequence of increasing atmospheric carbon dioxide, the only difference is that we do not feel or see the impacts as it is happening underwater. Atmospheric carbon dioxide is absorbed into the ocean and is converted into carbonic acid which lowers the ocean pH. This has been implicated in having adverse impacts on vertebrates, molluscs, corals and crustaceans (Wittmann and Pörtner, 2013), and it has also been suggest to have future impacts on fisheries (Cooley and Doney, 2009), food security (UNEP, 2010), sustainable development (UN-DESA, 2009). Subsequent blog post will talk about the impacts of ocean acidification on marine life.


Wittmann, A.C. & Pörtner, H. (2013) Sensitivities of extant animal taxa to ocean acidification. Nature Climate Change. [Online] 3 (8). p. 995–1001. Available from: http://www.iaea.org/ocean-acidification/download/9_Data%20Management/DMS%20pres/OA%20database_as_neededHPshort.pdf. [Accessed: 25 September 2014].

Cooley, S.R. & Doney, S.C. (2009) Anticipating ocean acidification's economic consequences for commercial fisheries. Environmental Research Letters. [Online] 4 (2), 024007. Available from: http://iopscience.iop.org/1748-9326/4/2/024007/fulltext/. [Accessed: 26 September 2014].

UNEP. (2010) Environmental Consequences of Ocean Acidification: A Threat to Food Security. UNEP Emerging Issues. United Nations Environment Programme. Nairobi: Kenya. Available from: http://www.unep.org/dewa/Portals/67/pdf/Ocean_Acidification.pdf. [Accessed: 26 September 2014].

UN-DESA. (2009) Ocean Acidification: A Hidden Risk for Sustainable Development. Copenhagen Policy Brief. [Online] 1. p. 1-4. Available from: http://sustainabledevelopment.un.org/content/documents/cop15_policy_brief_1.pdf. [Accessed: 26 September 2014].

Saturday, 11 October 2014

Cyanide fishing

Sea aquarium
Ever wonder how your sea aquarium fishes are caught? These marine fishes are caught by cyanide fishing. Unlike dynamite fishing, cyanide fishing does not physically destroy coral reefs, but rather killing the zooxanthellae algae in coral polyps. Although it is illegal, it is easy to carry out and escape detection, thus making it a popular fishing method for capturing live exotic fishes for aquariums or popular edible fishes (e.g grouper). Crushed sodium cyanide is mixed with salt water and stored in plastic bottles which divers bring down to squirt the mixture into nooks and crannies of coral reefs in order to stun the fishes. It was found that fishes that ingest cyanide developed cancer within 1 year of capture ( Earth Talk, 2011). Besides just affecting the fishes captured, cyanide poison fish eggs and kills other fishes (Mak, Yanase, Renneberg, 2005). It also poison coral polyps, killing zooxanthellae which is the provider of food and colour for the corals, thus resulting in coral bleaching. Furthermore, divers may physically break coral reefs in order to catch the stunned fishes that hide in crevasse
Cyanide fishing
Although cyanide fishing creates a lot of revenue for countries, the destruction it causes is more significant than its rewards. Coral reefs are depleting at a much faster rate than they can grow back. It is important that we protect marine life; they cannot protect themselves from humans. 


Earth Talk. 2011. How Dangerous Is It to Use Cyanide to Catch Fish?. [ONLINE] Available at:http://www.scientificamerican.com/article/cyanide-fishing/. [Accessed 12 October 14].

Karen K. W. MAK, Hideshi YANASE, and Reinhard RENNEBERG. 2005. Cyanide fishing and cyanide detection in coral reef fish using chemical tests and biosensors. Biosensors & bioelectronics. Vol. 20, No. 12, pp. 2581-2593.

Dynamite fishing

Dynamite fishing
Dynamite fishing is practiced in many countries and is a threat to marine animals and coral reefs in those areas. It involves throwing bottles of explosive made from fertilizers ( e.g potassium nitrate) into the sea. The explosion creates shock waves underwater, stunning or killing fishes, after which fishermen scoop the floating dead fishes from the surface or dive in to collect the fishes that sink to the seabed. However, besides just killing the targeted fishes, surrounding marine species and habitat are destroyed in the process. It is estimated that a 1 kg bottle bomb creates a crater of 1-2 meter in diameter, destroying 50%-80% of the coral reef in those areas ( Sea Shepherd, 2014). The coral reefs are reduce to rubble, turning the seabed into a "desert".

A 1 litre coca-cola bottle filled with explosive materials found near Capone island
This method is relatively cheaper and faster compared to other fishing methods. Local fishermen can easily make explosive from common fertilizes, aluminum blast caps and matchsticks. As a result, it is widely practiced by the poor and the greedy for easy money.

Blast fishing is illegal and destroy the marine ecosystem and habitat. Furthermore, fishermen are prone to injures and accidents through this method of fishing. We need to stop blasting fishes!


Sea Shepherd. 2014. Operation reef defense: protecting coral reefs worldwide. [ONLINE] Available at: http://www.seashepherd.org/reef-defense/destructive-fishing.html. [Accessed 12 October 14].