Threats to Marine Biodiversity

Marine Bio Exam 4

Invasive species

introduced species that survive and reproduce, and then negatively affect the habitats they invade, ecologically or economically

What regions do invasive species originate in

regions with similar abiotic conditions (ex salinity) This enables the invaders to survive while their population numbers are still low

Invasive species often achieve __

large body sizes and high population densities

Escape from the effects of natural enemies

Invasive parasite species in native and introduced ranges

Parasite species richness (left) and prevalence (right) was greater in native than in introduced populations

What makes communities more resistant against invasion?

Theory predicts that systems that are more diverse should be more resistant to invasion

High Species richness resists invasion …

increased species richness significantly decreased invasion success (A)

This is because more species rich communities, more completely and efficiently use limiting resources

declining biodiversity facilitates invasion, further accelerating loss of biodiversity

Communities are prone to invasion because

additional stress to community

Annual recruitment of introduced species was positively related to water temperature, whereas recruitment of native species was negatively related to water temperature

introduced species grew faster than native species at warmer temperatures (not pictured)

Causes of invasion

invasive species must be able to cross barriers that it would not naturally cross

related to frequency with which potential invaders arrive ex BALLAST WATER OF SHIPS provide frequent source of movement across long distances

What action can be taken? (Ballast Water)

Ballast water exchange involves replacing coastal water with open ocean water during a voyage

Process reduces the density of coastal organisms in ballast tanks that might invade recipient port

Major Causes of Pollution

a. Toxic substances - Metals
- Pesticides
- PCBs

- Oil

b. Nutrient sources - Sewage
- Fertilizers
- Animal waste

- Atmospheric sources

c. Debris sources - Fishing gear
- Plastics

d. Noise

Heavy Metals Mercury

reaches the ocean in low concentrations through natural weathering of rocks and volcanic activity

Discharges from industries, cities, and coal burning have increased the concentration of mercury in marine environment

Combines with organic chemicals to form organic compounds such as methyl mercury, which are particularly toxic

Methyl Mercury

accumulates in food chain. Older fish, higher in food chain, have higher mercury levels due to bioaccumulation.

humans eat fish containing mercury, they may suffer neurological disorders, paralysis and death

Other Heavy Metals

Cadmium – batteries and computers

Lead – batteries, paints, fuel additive

Copper – wood treatment other industries

Pesticides

usually designed to kill terrestrial insects, but they are carried to ocean by rivers (runoff)

As with heavy metals, they are taken up by plankton, then bioaccumulate and are magnified further up the food chain

Effect of Pesticides DDT on sea birds

High concentrations accumulate in body fat, interfere with reproduction, specifically deposition of calcium in eggs shells

some birds such as brown pelican and osprey faced extinction in 1970s

Polychlorinated biphenyls PCBs

derive from industrial activities and pose a major toxicity problem, especially in estuarine environments

bioaccumulates in food chains - cause reproductive failures

Oil

682 million tons of oil and derivatives enter each year as a result of pollution

584 million tons of oil enters the world oceans each year via natural seepage

Almost 85% of the polluting oil in US comes from storm water, river runoff, and fuel from small craft

Oil effects

short-term and long-term effects

Birds and mammals are particularly affected – many die of exposure

because oil covered fur and feathers loses its insulating propertiesRecovery estimates vary from 5 to 70 years

Minimizing oil pollution

Double-hulled tankers minimize loss of cargo in the event of minor accidents

Nutrient Sources

large additions of dissolved nutrients to coastal waters.

Principal known sources include:

• Sewage treatment outfall pipes
• Storm sewer overflows
• Commercial fertilizer – runoff from agricultural lands • Animal waste – runoff from agricultural lands
• Atmospheric deposition

Atmospheric Nitrogen

major source of nutrient addition to the ocean

Fossil fuel combustion is a major source of nitrogen oxide emissions

Gaseous emissions return to earth as soluble nitrates in precipitation

Eutrophication

ecosystem response to the addition of dissolved nutrients

ex phytoplankton bloom followed by hypoxia or anoxia - leads to crashes in population of zooplankton and nekton (die offs)

Development of die-off in an estuary:

a) Normal situation: phytoplankton is grazed and bottom waters are oxygenated

(b) Nutrient input stimulates phytoplankton growth and dead phytoplankton sink
– bacterial decomposition reduces oxygen content of water (hypoxia)

(c) Oxygen is removed (anoxia) from bottom waters and
benthic organisms die

Dead zones are a result of __

Nutrient addition to coastal waters

Reducing nutrient inputs by

Eliminating ocean dumping of solid sewage waste and better treatment of sewage before wastewaters are released into the coastal zone can abate eutrophication

treatment of sewage includes __

Primary treatment removes solids;

Secondary treatment removes toxic compounds;

Tertiary treatment removes nitrates and phosphates

But... it is expensive

Ghost Nets

fishing nets that have been abandoned or lost. Marine animals can still get caught and die (drown);
Nets and ropes can drag and destroy reefs and sessile organisms

Micro Plastics

tiny plastic particles (<5 mm) that result from both commercial product development and the breakdown of larger plastics.

Plastic is

non-biodegradable- it never does away, just gets smaller.

Microplastics have also been found to facilitate the transfer __

f contaminants when ingested.

noise pollution

can harm whales by damaging their hearing,
and in extreme cases, cause internal bleeding and death.

can cause behavioral changes

Major causes of habitat destruction

Coastal development: dredging; dumping of silt and mud; landfilling

Major drivers: growing cities; increased tourism; industrial development

major causes of habitat destruction beaches

Dredging/ Sand Mining:
Decimates communities living within sediment; suspends sedimentation in the area; buries top layer of sensitive beach communities

Major drivers: Beach grooming/ replenishment; digging out shipping routes

Major causes of habitats destruction mangroves

Mangrove removal: Destruction of mangrove forests; removing whole communities and ecosystem services (including coastline protection, flooding prevention)

Major drivers: Ocean view resorts, tourism; Vacation homes (typically not only home)

Trawling

trawls are dragged along the bottom to supply fish and shrimp to markets

Major drivers: government subsidies and customer demand for trawl caught fish

Deep sea mining:

excavating and harvesting resources from the deep sea bed Major drivers: precious metals, minerals and alternative energy sources for sustainable, electronic technology