Announcement***Seminar Today***

• “Lethal Sound: Submarines, Sonar and the Death of Whales”

• Joel Reynolds, Senior Attorney, Natural Resources Defense Council

• Tuesday Oct. 2 (TODAY) 5:00-7:00 pm

• Buehler Alumni Center

Overview of Human Impacts

Fishing and Overexploitation• Fish and shellfish are taken for a range of uses

including food, raw materials, medicines, pets and collections

• Fishing effort continues to increase with bigger and faster boats and better equipment

• Large percentages of many stocks are taken– In eastern U.S., > 90% of the eastern rock lobster is

harvested annually– In North Sea, 60-70% of the haddock is harvested

annually• 75% of the world’s fisheries are fully or

overexploited and 33% of the U.S. stocks are overfished or depleted

World’s Fisheries Catch

Fishing and Overexploitation

• Target species are managed in isolation typically with no management of resources they need

• Although impacts on populations often decline with abundance, fishing for particularly valuable fishes (swordfish grouper, tuna) may not

• Overfishing may result in serious declines and even endangerment of coastal benthic species (rockfishes) and species with vulnerable life histories (groupers)

By-catch or Incidental Take

• Many species are captured unintentionally with the target species

• These include many other taxa – Other fishes – Benthic invertebrates

– Marine birds, turtles, and mammals • The most serious problems with by-catch are

associated with methods like gill netting and bottom trawling

• Other methods such as long-lining are also associated with loses as well

Gill Netting

• Gill nets are enormous nets that are left adrift to capture fish

• Capture large numbers of open ocean fishes nonselectively

• Also drown birds, mammals and turtles

• Frequently lost, these nets can “ghost fish” for years

Bottom Trawling

• Trawling is among the most non-selectively fishing methods

• Trawling involves dragging nets along the bottom and captures fish nonselectively

• Finfish equal to 5-20% of the worlds entire seafood catch is caught in shrimp trawls

• Before 1981, U.S. by catch in shrimp trawls include 10 billion fishes and up to 55,000 sea turtles annually

Bottom Trawling

• Trawling also creates several types of disturbance

• Digging up deep sediments can result in death due to siltation of sponges and sensitive filter feeders

• Siltation can also affect light penetration and hence deeper water algal communities

Overexploitation

• Collection of species including fishes and invertebrates for aquarium trade

• Intense collections of particular species often by hand

• Unlike commercial fishing, when hand collected species become rare, value increases supporting continued exploit

• Economic projections indicate this will be an increasing trend in developing island countries in Asia

Coral Fishing

• Even smaller artisanal fishers often use techniques with large effects

• Dynamite fishing in coral reefs has damaged large areas of reef in the Indo-Pacific (e.g. Philippines, Indonesia)

• Sodium cyanide, bleach, and rotenone are also commonly used

• These kill corals reducing the local diversity of the whole system

More Than Just Fish

• Not just fishes but whales, seals, birds and turtles either are or have been heavily exploited

• Several groups have been exploited for food, oil, shells, feathers and other products

• Some of these (Caribbean monk seal, Japanese Sea Lion, Great Auk, Labrador Duck) have been driven to extinction

Marine Mammals

• Baleen whales and large toothed whales have been hunted for oil and meat

• Even smaller toothed whales including river dolphins and belugas have been hunted to very low levels

• Many Dall’s porpoise, bottlenose dolphins, pilot whales are taken as well

• In some cases, dolphins are killed and used as bait for other fisheries (crab, shark)

Sea Birds

• Sea birds have also suffered as well• Flightless birds like penguins are

particularly vulnerable• Ground and burrow nesters like

shearwaters, penguins, etc. are also very vulnerable

• Hunting for feathers and eggs has driven many species to near extinction

Turtles

• Six of the seven sea turtle species are threatened or endangered

• As a source of food, oil (leatherbacks) and aphrodisiacs (eggs)

• Shells and skins are also popular for collectors

• Beach nesting makes these species particularly vulnerable

Extinct Marine Species

From Carlton et al. 2003. Annual Review of Ecology and Systematics

Habitat Alteration

• A wide range of human alterations to coastal landscapes regularly occurs

• Dredging and channeling • Beach nourishment and grooming• Construction of jetties, levies and breakwaters• Anchoring and trampling• Logging and mining• Coastal development

Habitat Alteration

• Creation of shoreline structures has many unintended consequences

• Structure like jetties, levies, rip rap, breakwaters, seawalls destroy habitat

• Structures like jetties create down shore erosion

• Structures like seawalls can prevent migration of marshes and sea grasses as sea level rises

Habitat Alteration

• Beach nourishment involves impacts to both the source and deposit areas

• Mining sand resuspends sediments, changes current and erosion patterns and can remobilize pollutants

• Adding sand can also resuspend sediments and add to siltation loads

• Beach grooming (seaweed removal) can impact shore species and remove nutrients for high beach habitats

Habitat Alteration

• Anchoring and trampling of areas is common in tourist areas

• Anchoring by recreational fishing and diving boats can significantly impact areas of slow growing coral reefs

• Trampling of marshes, beaches and intertidal cobble habitats can result in “loving to death” favorite areas

Habitat Alteration

• Dredging and channeling can have significant short and long term impacts

• Channeling can lead to erosion and subsidence in estuaries and other soft sediment habitats

• Dredging resuspends fine silts that clog and kill sensitive filter feeders

• Dredging and channeling may mobilize pollutants

• Sediments and changing flow may produce areas that can become hypoxic (low O2) or anoxic (no O2)

Habitat Alteration

• Extractive activities like logging and mining have multiple impacts

• Logging mangrove forests is happening worldwide

• In addition to the outright loss of habitats, loss of mangroves can exacerbate coastal erosion

• Mining and drilling can also cause sediment resuspension, loss of habitat and chemical pollution from drilling wastes (contaminants)

Habitat Alteration

• Coastal development can also have multiple impacts in coastal and neashore areas

• Development and land use changes can increase siltation and sediment transport

• Especially important in low silt habitats like coral reefs

• Freshwater inputs are also important– Loss of freshwater (San Francisco Bay)– Too much freshwater from increased runoff

Biological Invasions

• Human activity has increase the rate of introduction of non-native species

• It a natural process (like extinction) that we have greatly increased (x 106)

• Biological invasions have a range of impacts from immeasurable to devastating

• Introductions in the ocean are largely irreversible• Impacts are difficult to predict in advance

Biological Invasions

• Introduced species can impact human recreation– Algal blooms can make beaches unusable– They can clog nets used by sport and commercial

fishers

• Introduced species can influence ocean water quality– Blooms of introduced phytoplankton can create red or

brown tides

• Can cover or damage aids to navigation, water intakes, docks/piers/pilings– Sessile invertebrates can rapidly cover hard surfaces

Biological Invasions

• Invasions can result in loss ecosystem function and ecological extinction

• Habitats can changed entirely: – Introduced plants can occupy open space or change

the primary producer base (Caulerpa seaweed, Spartina alterniflora cordgrass)

– Introduced filter feeders (Asian mussel, like zebra mussel) can remove plankton needed for others in food chain

– Introduced predators may drive species to near extinction

– Introduced diseases can devastate native populations

Biological Invasions

• Coastal areas, particularly estuaries are among the most heavily affected

• Even relative pristine areas like coral reefs have invasive species problems

• In San Francisco Bay, >90% of benthic biomass is introduced

• A new species arrives every 12 weeks• Creates loss of beta diversity, functional

extinction and potential for outright extinctions

Spartina Invasion in San Francisco Bay

Diseases

• Diseases are important and episodic• Many diseases occur naturally, but their

frequency and extent can be altered by human activities

• Other human mediated stressors (temperature, contaminants, etc.) can create epidemics

• Human activities can also result in new diseases like Toxoplasma pathogen (transmitted to pinnipeds from cat litter disposal)

• Some pathogens have been implicated in coral diseases and even bleaching

Diseases

• Disease epidemics may also occur as the result of selective over fishing

• Oysters in Chesapeake Bay crashed due to diseases beginning in the 1960’s (the diseases may also be introduced)

• Selective fishing likely removed the largest/most vigorous oysters leaving the smallest/less vigorous

• Generations of selection may leave population vulnerable

Diseases

• Climate change can interact with disease– Band diseases (white band, yellow band, black band)

of corals is closely correlated with temperature• Siltation and contaminants are also exacerbate

disease– Increased tumors in fishes and shellfish in urban

harbors • Land use change and desertification may also

affect disease– Increased dust from Africa transported by winds to the

Caribbean exacerbate coral disease

Contaminants

• A wide range of contaminants affect marine habitats almost everywhere

• These include not just petroleum, but radio nucleotides, organics, metals, pesticides, herbicides and solid waste

• Most systems are impacted by more than one compound

• Effects of multiple contaminants are very difficult to assess

Contaminants

• Oil drilling and transport results in oil contamination on small and large scales

• Damage due to poisoning, coating, asphyxiation– Seabirds, otters, pinnipeds at special risk

• Light fractions can be very toxic– Affect invertebrates, floating eggs at surface

• Also toxic drilling muds – Regularly released from offshore gas and oil

Contaminants

• Coastal industries and agriculture are big contributors to this problem

• Non-point source pollutants include pesticides/herbicides as well as nutrients from farms and ag fields

• Some chemical contaminants are the result of older point sources (factories)

Contaminants

• PCBs, PAHs, and others are often the result of older point sources associated with factories

• Many older point sources have come into compliance with current laws

• Many organic compounds are long lived or have accumulated in another form and can be remobilized over time

Contaminants

• Nutrients like nitrates and phosphates in large quantities are also pollutants

• Enter waters from non-point sources like farms, vineyards, lawns, sewage effluent, atmospheric deposition

• Eutrophication is an enormous problem in many coastal areas– Baltic Sea, Adriatic Sea, Arabian Gulf, New

York Bight

Contaminants

• Solid waste or trash occurs throughout the world’s oceans

• Plastic debris kills unknown numbers of birds, turtles, marine mammals

• Ghost fishing from abandoned traps also has significant impacts in sensitive areas (e.g. Northwestern Hawaiian Islands)

• Up to 7% of the stock in the lobster fishery• Lost gill nets also have similar effects

Climate Change

• Human activities are also resulting in changes to the atmosphere and climate

• These changes include:– Increase in UV-B– Increase (and decrease) in surface

temperature– Changes in circulation– Altered storm and rainfall patterns– Rising sea levels

Climate Change

• UV-B radiation due to loss of stratospheric ozone

• CFCs (chlorofluorocarbons) and related compounds migrate to stratosphere and degrade ozone for many years

• Can cause population reductions in some phyto- and zooplankton and increase mortality in larval fishes

• Effects on plankton in particular could influence entire food web

Climate Change

• CO2 , methane and other green house gases by most estimates are increasing global temperature

• Warming of sea surface temperatures will have many impacts

• Affect winds, surface and deep ocean currents, habitats and organisms

Climate Change

• Temperature most important in shallow areas and in poles (predicted to warm more)

• Corals and zooxanthellae symbionts are close to their thermal limit

• Coral bleaching is highly correlated with increased ocean temperatures

• May also result is shrinking of sea ice systems and movement of sea-ice borders

Climate Change

• Changing temperatures can influence wind patterns and thus ocean circulation

• Could negatively influence upwelling areas such as along the California coast

• May change deep ocean currents produced by sinking of saline polar waters

• Changes in ocean circulation may alter equilibration of global temperature

Climate Change

• Increased melting of glaciers and polar ice packs is resulting in rising sea levels

• In addition to threatening coastal cities it may negatively effect marshes, sea grasses, mangroves and other low elevation habitats

• Changes in coastal land use may not allow habitats to migrate and will result in loss of habitat

• Rising sea levels may drown slow growing corals that cannot grow fast enough to keep up

Climate Change

• Global change can interact with other stressors

• Impacts and occurrence of invasions, disease, and contaminants can all be multiplied by increased temperature, siltation, nutrients, etc.

• Changes are moderate now, but possibility of state change with rapid temperature increase in the future (more later on isotope stage 11)