Marine Ecosystems and Biodiversity

• Marine ecosystems and biodiversity cover key terms such as ecosystem, habitat, population, species, biodiversity, and ecological niche

Key Definitions:

• Habitat: An organisms place of residence, such as a hydrothermal vent for tube worms
• Ecosystem: The symbiotic relationship between organisms and non-living factors, for example: a rocky shore
• Population: A group of the same species living in one area, for example: ghost craps
• Community: All species that share an area at the same time
• Species: Similar organisms that can breed and create fertile offspring, such as skipjack tuna
• Biodiversity: The number of different species in an ecosystem
• Ecological niche: An organisms role in an ecosystem
• The overlap of ecological niches can lead to competition

Relationships Within a Marine Ecosystem:

• Mutualism: An affiliation between species that benefits each, such as coral and zooxanthelle, cleaner fish and groupers, and chemosynthetic bacteria and tube worms
• Parasitism: An affiliation between two organisms where one benefits while hurting the other, such as tuna and nematodes
• Ectoparasites: Parasites residing outside the body, for example fish lice
• Endoparasites: Parasites residing inside the body, for example nematodes

Food Chains and Food Webs:

• Producer: Organisms that synthesize organic substances, like photosynthetic plankton and chemosynthetic bacteria at hydrothermal vents
• Consumer: Organisms that get energy by consuming other organisms, such as herbivores and carnivores
• Predator: An animal that hunts, kills, and consumes other animals, such as sharks and octopuses
• Prey: An animal that is caught, killed, and consumed by another, such as seals and anchovies
• Trophic Level: The feeding levels in a food chain or web
• First trophic level: Producer
• Second trophic level: Whatever consumes the producer and on it goes...
• Chemosynthetic bacteria at hydrothermal vents produce organic substances through the oxidation of hydrogen sulphide

Predator-Prey Interrelation

• Prey population increase leads to predator population increase
• The opposite is also true

Shoaling

• Large populations of the same species and approximate size are referred to as shoals
• Tuna and sardines shoal
• Shoaling increases hydrodynamic efficiency as it saves energy to swim in a large group by reducing drag
• Shoals may confuse predators; more eyes are on the lookout for predators
• Shoaling increases foraging efficiency by decreasing time to find food
• Shoaling is a reproductive advantage, increasing the opportunity to find a mate

Ecological Succession

• Succession: The gradual change of an ecosystem over time
• An example of succession can be seen in hydrothermal vents:
• Bacteria first grows near the vent.
• Tube worms like Tevnia arrive first.
• The larger, quicker-growing Riftia replace Tevnia over time

Biodiversity

• Stable environments such as coral reefs have high biodiversity
• Unstable environments like sandy slopes of coral reefs have low biodiversity, as they erode easily, dry out and are subject to changing conditions
• Extreme environments like hydrothermal vents have extremely high temperatures and pressures, further restricting the biodiversity
• Specialised niches belong to organisms with very specific food requirements or habitat, for example: coral eating butterfly fish which only feed on a few species of coral and anemone
• Tuna have generalised niches because they inhabit the open ocean and consume a wide range of fish species
• High biodiversity habitats tend to contain narrow ecological niches.

Marine Ecosystem Energetics

• Photosynthesis captures sunlight energy, making it available to the food chain
• Chemosynthesis captures the chemical energy of dissolved minerals
• Chemosynthetic bacteria at hydrothermal vents have a mutualistic relationship with tube worms
• Productivity is the rate of biomass production described in joules/ m2/ year and affects all trophic levels.

Food Chain Energy Loss

• Only a small percentage of sunlight energy is captured and used for photosynthesis
• Approximately 10% of energy is transferred to the next trophic level
• 90% of energy is lost due to respiration, heat loss, death, and waste
• Ecological pyramids have producers at the bottom and horizontal bars representing trophic levels
• Bar width is proportional to numbers, biomass, or energy.

Nutrient Cycles in Marine Environments

• Nutrients dissolve in the oceans surface layer
• Reservoirs of dissolved nutrients are replenished by:
• Upwelling: water from deep water brings nutrients to primary producers
• Runoff: Water leaches nutrients from soil, delivering them to rivers
• Atmospheric dissolving gases: carbon dioxide and nitrogen reach the surface
• Primary producers deplete dissolved nutrients during photosynthesis
• Productivity is directly related to available dissolved nutrients
• Nutrients in food chains sink to the sea floor in feces or after death, may be incorporated into coral reefs or harvested
• Nitrogen is used in protein
• Carbon is used to make carbohydrates
• Magnesium is used to make chlorophyll
• Calcium is used to make bones, coral, and shells
• Phosphorus is used to make DNA and bones

Coral Reefs and Lagoons

• The Darwin-Dana-Daly theory of atoll formation is as follows:
• Oceanic volcanoes rise from the sea forming an island
• Fringing reef develop around the island
• The island subsides to form a barrier reef
• The island disappears leaving an atoll
• Silt reduces light penetration
• Coral require suitable substrate to attach to made of mostly basaltic rock

Three Types of Reefs are:

• Fringing
• Barrier
• Atoll
• Needed coral growth conditions are temperatures of 16 - 35°C, but 23 - 25°C is optimal.
• Coral reefs absorb wave energy to protect from erosion, protect coastal properties and ecosystems, reduce the cost of breakwaters, provide safe anchorage, and have economic advantages
• Factors leading to reef erosion: predation by the crown-of-thorns starfish, storm damage, and exposure to air
• Artificial reefs act as submerged breakwaters, dissipate wave energy, reduce coastal erosion, protect anchored boats, and provide economic growth to the area

Reconstruction Methods

• Geomorphology: the study of landforms and processes that shape them.
• Techniques used to understand the history and growth of coral reefs include:
• Deep Drilling: cores of materials can identify corals and estimate growth using bands
• Carbon Dating: the proportion of C14 to C12 in a sample can estimate the age of coral up to 50,000 years

Sea Level Changes

• Fossil corals found at depths of 1200 m are evidence of subsidence
• Fossil coral found above sea level is evidence of changing sea levels

Plate Tectonics

• Alfred Wegner proposed the theory of continental drift and Pangea
• The outer crust of Earth, the lithosphere, is made of plates floating on the asthenosphere, moving slowly relevant to each other.
• This movement produces convergent, divergent, and transform plate boundaries
• Evidence for plate tectonics: the fit of coastlines of South America and Africa, fossil distribution, paleomagnetism, glacial scarring, and coal in Antarctica

Tectonic Processes

• Ocean trenches form along convergent boundaries where subduction occurs, like the Challenger Deep.
• Mid-ocean ridges are underwater mountain ranges at divergent boundaries formed by magma upwards that undergoes sea floor spreading
• Hydrothermal vents occur in the deep ocean near mid-ocean ridges, where seawater seeps into cracks and is released from magma
• Abyssal plains are flat areas of the ocean floor between trenches and continental rises which are formed by the upward movement of molten material covered in sediments.
• Volcanoes are openings in the Earth's crust so that hot gas and magma release, most activity is submarine.
• Earthquakes are a sudden release of energy in the Earth's crust that create seismic waves, and cause great tension releasing it during a slip
• Tsunamis are long wavelength waves produced by a large volume of water's movement and slow down near the coast as the destructive wave forms

Hydrothermal Vents

• Water coming from hydrothermal vents is under pressure, hot, and rich in minerals
• Cold water seeps into cracks and is heated by magma
• This causes water to force back up to the ocean floor carrying dissolved minerals
• Temperatures may exceed 100°
• Isostasy may produce shallow seas because the Earth's crust is higher where its thicker and less dense, and lower where its thinner and denser
• Continental crust is denser than oceanic crust

Littoral Zone

• The littoral zone is between the high water mark of the coast and the lowest part of the shore permanently underwater
• Rocky shores are resistant outcrops of rock that are the most exposed and resistant to erosion
• Sandy shores are formed by the erosion of sandstone and deposition of sand
• Muddy shores are the least exposed to erosion
• Estuaries are semi-enclosed coastal bodies with brackish water
• Deltas are formed when a river with sediments reaches a large body of water and settles in triangular formations
• Factors like mangroves in tropical/subtropical saline habitats with pneumatophores, and sandy and rocky shores form ecological communities in the littoral zone

Environmental Factors

• Rocky shores have high biodiversity, stability, and clear zonation
• In rocky shores, animals resist desiccation
• Environmental factors include desiccation, temperature, wave action, and light intensity
• Additional factors include slope, aspect, and substrata

Ocean Composition

• Seawater has a salinity of 35%.
• Precipitation, freshwater, and melting glaciers can dilute seawater.
• The ocean's chemical composition is relatively constant
• Composition changes locally due to volcanic activity and atmospheric dissolution
• Submerged volcanoes release gases like chlorine
• Runoff flows from land into the ocean
• Gases in seawater are at equilibrium, concentrated by the waters temperature and salinity
• Evaporation increases salinity
• Salinity is the measure of salt concentration in water
• Temperature gradients produce dense water
• As temperature increases, density decreases, forming a layer
• Decreasing temperature creates a thermocline
• As salinity increases, density increases
• Lower salinity floats on top, increasing with depth, creating a halocline
• Wind blowing across the surface or temperature decrease causes mixing
• Turbulence and waves mix oxygen
• Algae increases dissolved oxygen by photosynthesis, and marine animals decrease it by respiration
• Dissolved oxygen is high at the surface
• It drops to the oxygen minimum layer, then rises again

Ocean Tides

• Tides are the regular rise and fall of sea level due to gravitational effects of the Sun, Moon, and Earth's rotation
• In coastal areas, there's two high and low tides per day
• Spring tides: The Sun, Moon, and Earth are arranged in a line.
• Neap tides: The Sun, Moon, and Earth are at right angles
• Shape and slope of the coastline, body size, weather, air pressure, and winds affect the tidal range
• Ocean currents move continuously, driven by waves, winds, the Coriolis Effect, temperature, salinity, and tides
• Surface ocean currents are driven by winds and have a spiral from the Coriolis Effect
• Deep ocean currents are driven by temperature and density gradients
• Upwelling areas cause vertical movement of water

El Nino:

• El Nino is an event in the southern Pacific Ocean
• Normal El Nino conditions: cold, nutrient-rich water flows northerly with upwelling and winds from the south, and results in high productivity and a large fishing industry
• El Nino conditions: Prevailing winds stop blowing, equatorial water blows by west winds, reversing Pacific's pressure gradients and wind directions
• This creates warm water, prevents upwelling, depletes nutrients, results in a drop in water species, and is disastrous to the fishing industry.

Monsoons

• Asian continent and Indian Ocean temperatures give rise to monsoon winds
• A monsoon is seasonal in the Indian Ocean
• The sea is warmer than land in winter, rising air draws cooler air from land
• In summer, the pattern reverses with warmer temperatures over land pulling in air from the ocean
• Summer Monsoons bring thunderstorms and heavy rain
• Tropical cyclones are storm systems with a low-pressure center, thunderstorms, strong winds, and heavy rain
• Cyclones develop over warm water and low pressure areas when water evaporates
• As water rises and condenses it releases heat which increases evaporation and drives cyclone development
• Coriolis Effect causes spinning
• Tropical cyclones are known as Hurricanes in the North-Atlantic, typhoons in the north-west Pacific, and willy-willy's in Australia

Negative Cyclone Effects

• High winds damage coastal property and boats, and erode land
• Heavy rainfall floods communities and drowns
• Storm surges flood low-lying land

Positive Cyclone Effects

• Rain can benefit arid areas
• Surges replenish nutrients and increase aquatic productivity