Aquatics - Adaptations

There are lots of types of aquatic habitats, and aquatic creatures are adapted to their specific natural habitat. We therefore need to cater for these needs of captivity.

• saltwater
• cover more than 70% of the Earth's surface
• almost 7 miles deep at its deepest point
• animals that live in the bathypelagic zone may never see sunlight
• not many nutrients
• e.g., yellowfin tuna, blue whale

• brackish
  • often tidal so can become more salty
• provides protection, lock up carbon, and are important for birds
• e.g., juvenile lemon sharks, mudskippers

• freshwater (seasonal)
• not a permanent structure
• good sheltered areas
• can be found in floodplains
• e.g., piranha

• saltwater/freshwater (brackish)
• river meets sea
• lots of nutrients
• lots of protection
• lots of fish nurseries
• need to be adapted to change
• e.g., eels, starfish, crabs

• saltwater
• 0.1% of the Earth's surface is coral reef
  • 25% of Earth's species on coral reef
• most consistent aquatic habitat
• the fluorescent colours can act as sun blocks that protect resident zooxanthellae in the tissues of shallow water corals from harmful sun rays
  • in deep water corals fluorescence creates additional light for the zooxanthellae
  • fluorescence can indicate the health of a reef
• water poor in nutrients
• their health is dependent on clean, clear water, and abundance of sunlight, and a common water temperature of 25-30°C
• Bounded by latitudes 30°N and 30°S
  
• coral reefs are in trouble due to bleaching as the temperature rises
• e.g., triggerfish, pufferfish, yellow tang, clownfish
• tube-dwelling anemones resemble sea anemones, but they lie buried in soft sediment an can pull back into a tube
  • have two whorls of tentacles, the outer whorl captures food and the inner whorl of smaller tentacles manipulates the food

• On coral reefs there is a chorus in the morning and evening, with sounds being louder in the evening
  • greatest intensity during the new moon and lowest intensity during a full moon
  • coincides with times of the greatest activity on the reef
  • the quietest sounds are the sounds of urchin teeth as they feed and a faint rasping of spines rubbing together, the globular shell/'test' of the urchin acts as an amplifier
  • the loudest sounds, which often drown out the others, are from the snapping or pistol shrimps
• sea turtles have been known to use coral reefs to get cleaned by fish

• saltwater
• nutrient rich
• small bodies of water can evaporate and made very salty

• freshwater
• constant change
• e.g., pike, salmon, trout, eels

• freshwater/saltwater
• some are nutrient rich, some are nutrient poor
• some are diverse and some have a small amount of species

• freshwater
• may be more seasonal
• provides lots of shelter
• generally, a good amount of nutrients

• specialised fins
• feeding types
• body shapes
• colouration
• limbs
• lungs
• aestivation = summer hibernation

• Lepidogalaxias salamandroides
• found in western Australia
• buries underground during dry seasons to find ground water
• goes through aestivation
• exchange gases through their skin and store urea

• a sub-order of ray-finned freshwater fish
• lung-like labyrinth organ as part of the gills
• take oxygen direct from the air and into the bloodstream
• survive for short period out of water
• labyrinth organ develops as they age

• freshwater fish in the subclass Dipnoi
• lungs which are connected to the larynx and pharynx without a trachea
• lungs have smaller air sacs to maximise the surface area
• during the dry season the African lungfish creates a mucous cocoon to survive out of water for up to a year

• have the ability to walk out of water

• In 2015, global plastic production exceeded 320 million metric tons
• In 2015, between 4.8 to 12.7 million tons ended up in the ocean as a result of poor waste management
  • by 2025 (correct as of 2016) it is thought there will be 1 ton of plastic for every 3 tons of fish in the ocean
• substantial concern over macroplastic debris
  • e.g., fishing nets, plastic bags, drinks containers
• increasing abundance in microplastics
  • can be as small as a virus
  • now found worldwide
• estimated every square kilometre of the world's oceans has 63,320 microplastic particles floating on the surface
  • in some places this is 27 times higher
• microplastics come from incomplete degradation of larger plastic pieces, microbeads found in skin cleansers, toothpaste, shaving cream, abrasives used to ***** paint and remove rust, fibres from synthetic fibres and mechanical abrasion of car tyres on roads.

• Plastics adversely affect terrestrial and marine ecosystems on both macro and micro scales
  • nearly 700 marine species have been reported to either ingest and/or become entangled in plastic
    • includes 50% of all sea birds, sea snakes, penguins, seals, sea lions, manatees, sea otters, fish and crustaceans
• Plastics contain chemicals that, when eaten, can lach out and disrupt normal hormonal function
• microplastics absorb a wide array of organic and inorganic pollutants from the surrounding environment
• ingestion of microplastics by marine zooplankton at the bottom of the food chain is magnified higher up the food chain, where toxins accumulate and concentration is increased

• The Arctic Ocean between Greenland and Norway, and the Southern Ocean around Antarctica, are both areas where cooling and higher salinity makes the seawater at the surface dense enough to sink into the abyss to form the descending currents of the ocean's global circulation system
  • Predictions are that global warming will cause surface ocean waters in these polar regions to become warmer and less  dense and tus less likely to sink
• a stronger hydrological cycle, alongside ice sheet melting, will lower the salinity of polar surface waters
• these factors could weaken the ocean's overturning circulation or even make it collapse
• ice sheet melting
  • Greenland ice sheet shedding nearly 300 billion tons of water a year into the North Atlantic
  • Raise global sea levels
  • Weaken deep ocean circulation by adding huge volumes of fresh water
• ocean circulation in the North Atlantic has seemed to slow in recent decades, but it is currently unclear whether this is related to climate change or part of the natural cycle of faster and slower currents

• Could have major consequences on regional climates and ocean ecosystems if circulation slows or changes flow direction
• Data from the geological past shows that if the North Atlantic circulation slows or shuts down the entire Northern Hemisphere will cool, the Indian and Asian monsoon areas will dry up and less ocean mixing will result in less plankton and other life

• Oceans absorb additional carbon dioxide emitted into the atmosphere by the burning of fossil fuels
• Absorption of carbon dioxide increases ocean acidity by a series of chemical changes and reduces the availability of molecules essential for calcium carbonate shell formation
• The oceans ability to hold carbon dioxide is affected by temperature
  • cold water holds more carbon dioxide than warm water
• because of warming water, the ocean is able to absorb less carbon dioxide from the atmosphere
  • more carbon dioxide in the atmosphere
• when carbon dioxide dissolves in the ocean it produces carbonic acid
  • makes the ocean more acidic
• carbonic acid binds up with carbonate ions, the essential building blocks for shell formation 
  • reduces availability of carbonate ions means more investment in shell making activities
    • hampers growth of organisms such as corals, oysters, clams and mussels
• many species of plankton are making thinner carbonate shells
  • important because they form the base of marine food webs
• shell forming marine creatures face two potential threats
  • unable to build robust shells
  • shells dissolve more readily as the ocean acidifies and becomes more corrosive

• Continued ocean acidification will lead to coral reefs corroding faster than tehy can be rebuilt.
  • threatens long term viability
  • estimated one million species rely on coral reefs for survival
• results in reductions in the spawning and larval growth of fish, the oxygen carrying capacity of blood in squid and predator-avoidance behaviour in sea urchins and fish
• Plants and many algae flourish in a high carbon dioxide world, however, future increases in coastal pollution may counteract this potential benefit
• the current rise in atmospheric carbon dioxide can impact ocean acidity and does not allow time for organisms and ecosystems to adapt
• ideas being explored to alleviate the pressure include addition of neutralisers to the oceans, and the capturing and safe storage of atmospheric carbon dioxide

• Marine planktons consists of microscopic algae and bacteria (phytoplankton) and animals (zooplankton)
  • phytoplankton forms the base of marine food webs
  • zooplankton eats phytoplankton
  • zooplankton can be the larval form of larger animals
• zooplankton is eaten by larger predators, ranging from small fish to whales
• Phytoplankton have chlorophyll and through photosynthesis use sunlight to produce organic carbon compounds in the form of soft tissues, releasing oxygen as a by-product.
• Organic matter and shells of calcifying plankton settle to the ocean floor when phytoplankton and calcifying plankton die
• Organic matter is lighter than sea water so its vertical transport is through absorption at the surface of other falling particles such as shell fragments, dust, sand and faecal matter
• Falling particles of dead plankton and other organic materials = marine snow
  • resemble snowflakes falling from the upper ocean
  • majority disintegrates during the journey to the ocean floor
    • only 1% makes it to the deep ocean where it provides food for deep sea creatures
    • the small percentage not consumed is incorporated into ocean floor sediments

• About 3/4 of the deep ocean floor is covered with sediment that can reach up to 1km thick
  • marine snow transports carbon captured at the surface into the deep and is part of a biological carbon pump
  • Carbon dissolved into the deep waters is locked away for thousands of years
    • carbon buried in sediment is locked away for millions of years
• Each of the hundreds of thousands of phytoplankton that live in the Earth's oceans are adapted to particular sea water conditions
  • changes in temperature, clarity, nutrient content and salinity affect diversity and abundance of phytoplankton
  • in response to increasing temperatures and acidity phytoplankton in polar regions are becoming more diverse and ones in tropical regions becoming less diverse
• as surface waters warm there is less vertical mixing to recycle stored nutrients from the deep waters back to the surface
  • complex effects on marine food webs, carbon capture and oxygen production not completely clear
    • could result in the abundancy and diversity of all life in the ocean being under threat.

• The concentration of carbon dioxide in our atmosphere continue to rise
• The spring of 2014 was the first time in probably the last 2.5 million years that levels of carbon dioxide exceed 400 parts per million
  • this has been driven by fossil fuels
  • before the industrial revolution carbon dioxide concentrations were about 270 parts per million, and had been consistently at that level for 10,000 years
• today there is 60 million times more carbon in the deep ocean that in the atmosphere
  • this is one of the main controls of carbon dioxide levels in the atmosphere
  • oceans have absorbed at least one-quarter of the excess carbon dioxide generated by human activities
• the rate of carbon dioxide release from fossil fuels will determine how much carbon dioxide can be absorbed by the ocean
  • too fast and the ocean will not be able to keep peace
  • the current rate of release is overwhelming the upper ocean sinks
  • over long timescales of 1000 years or more, our carbon dioxide pollution will slowly be transferred to the deep ocean but this slow process only happens in isolated polar regions where surface waters sink into the abyss
  • over timescales of 1000 to 10,000 years the excess carbon dioxide will be neutralised by a reaction with the abyssal sea-floor sediments

• One solution to our carbon dioxide problem is to burn fewer fossil fuels, but we need to try remove the carbon dioxide that is already put into the atmosphere.

• the problem with fishing is that sometimes fisheries will take fish without ensuring there is a reliable supply of replacement animals
• as the human population has increased, so has the pressure on fish stock. Over the last century there has been significant overfishing in a range of species
  
• another issue of fishing is 'bycatch', where species that are not wanted are discarded after being killed in fishing gear
• the UN Law of the Sea treaty determines where states can fish, but it is not binding on states that have not ratified or acceded to it, such as the USA.
• Fish are mobile and at many points during their lifetime they can pass through the legal responsibility of many states
  • managing marine stocks is challenging
• many experts believe that we must aim to allow fish populations to rise, even if that means reducing our current exploitation rates
• we must restrict human activities such as commercial fishing and mineral developent using laws. We must create Marine Protected Areas (MPAs) to limit shopping and reduce both local pollution and acoustic noise
  • studies of MPA effectiveness show they consistently improve biodiversity and fish stock numbers
  • How much human activity can be restricted depends on the location of the MPA

• the largest MPA is currently an area of 1.5 million square kilometres of the Ross Sea in Antarctica
• About 2% of Oceans are protected by MPAs
• The United Nations Convention of the Law of the Sea (UNCLOS)
  • coastal states have a territorial sea out to 12 nautical miles (1 nautical mile = 1.852km)
  • out to 24 nautical miles states can enforce a contiguous zone, which is important for immigration, pollution, customs and taxation
  • for 200 nautical miles from the baseline, states have an exclusive economic zone where they have rights to natural resources
  • outside this is international waters where no state has control
  • where states are closer than 200 nautical miles apart, boundaries lie at the mid-point between them (median line)