Marine Resources: Exploring Oceans' Impact on Biodiversity, Climate, and Economy, Slides of Environmental Science

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Marine and Coastal Resources Chapter 16 Environmental Science docsity.com Oceans cover most of the Earth’s surface • The oceans influence global climate, much biodiversity, facilitate transportation & commerce, and provide resources • Cover 71% of Earth’s surface and contain 97.5% of Earth’s surface water docsity.com Ocean water flows horizontally in currents • Currents = the ocean is composed of vast river like flows – driven by density differences, heating and cooling, gravity, and wind – influence global climate – transport heat, nutrients, pollution, and the larvae of many marine species • Some currents such as the Gulf Stream are rapid and powerful – the warm water moderates Europe’s climate Currents video docsity.com Surface winds and heating create vertical currents • Upwelling = the vertical flow of cold, deep water towards the surface – high primary productivity and fisheries – also occurs where strong winds blow away from, or parallel to, coastlines • Down-wellings = oxygen-rich water sinks where surface currents come together docsity.com Open ocean systems vary in biodiversity • Microscopic phytoplankton constitute the base of the marine food chain in the pelagic zone – algae, protists, and cyanobacteria • These organisms feed zooplankton – which then feeds fish, jellyfish, whales, etc. • Predators at higher trophic levels include larger fish, sea turtles, sharks, and fish- eating birds docsity.com Coral reefs are treasure troves of biodiversity • Located in shallow subtropical and tropical waters • Corals = tiny colonial marine organisms – related to sea anemones and jellyfish – remain attached to rock or existing reef and capture passing food with stinging tentacles docsity.com Coral reefs consist of millions of corals • Coral reef = a mass of calcium carbonate composed of the skeletons of corals – consists of millions of densely packed individuals – protect shorelines by absorbing waves – invertebrates and fish species find food and shelter in reef nooks and crannies docsity.com Intertidal zones undergo constant change • Intertidal ecosystems = where the ocean meets the land – between the uppermost reach of the high tide and the lowest limit of the low tide • Tides = periodic rising and falling of the ocean’s height due to the gravitational pull of the sun and moon – intertidal organisms spend part of their time submerged in water and part of their time exposed to sun and wind docsity.com Salt marshes occur widely • Salt marsh = occur along coasts at temperate latitude – tides wash over gently sloping, sandy, silty substrates – high primary productivity – critical habitat for birds and commercial fish and shellfish species – filter pollution – stabilize shorelines against storm surges docsity.com Mangrove forests line coasts • In tropical and subtropical latitudes – replace salt marshes along sandy coasts • Mangroves = trees with unique roots – curve upwards for oxygen – curve downwards for support • nurseries for commercial fish and shellfish • nesting areas for birds • food, medicine, tools, construction materials docsity.com Estuaries: where fresh and salt water meet • Estuaries = water bodies where rivers flow into the ocean – wide fluctuations in salinity • Critical habitat for shorebirds and shellfish • Transitional zone for fish that spawn in freshwater and mature in salt water • Affected by development, pollution, habitat alteration, and overfishing 17 docsity.com Marine pollution threatens resources • Even into the mid-20th century, coastal U.S. cities dumped trash and untreated sewage along their shores • Oil, plastic, chemicals, excess nutrients make their way via runoff from land into oceans • Raw sewage and trash from cruise ships • Abandoned fishing gear from fishing boats docsity.com Nets and plastic debris endangers marine life • Plastic items dumped into the sea harm or kill wildlife • Plastic is non-biodegradable – drifts for decades – washes up on beaches – wildlife eat it or get entangled and die • The 2006 Marine Debris Research, Prevention and Reduction Act docsity.com Oil pollution comes from spills of all sizes • Major oils spills – 1989 Exxon Valdez – 2010 Deep Water Horizon • Cause serious environmental and economic problems: – Foul beaches – Coat and kill animals – Devastate fisheries Exxon Valdez docsity.com Excess nutrients cause algal blooms • Harmful algal blooms = nutrients increase populations of algae that produce powerful toxins • Red tide = algal species produce reddish pigments that discolor water – illness and death to wildlife and humans – economic losses to fishing industries and beach tourism • Reduce runoff and prevent consumption of affected organisms docsity.com Overharvesting is the worst marine problem • Unprecedented pressure on marine resources – Half the world’s marine fish populations are fully exploited – 28% of fish populations are overexploited and heading to extinction • Total fisheries catch leveled off after 1998, despite increased fishing effort • Predicted that populations of all ocean species we fish for today will collapse by the year 2048 docsity.com We have long overfished • People began depleting sea life centuries ago • Some species hunted to extinction: Steller’s sea cow, Atlantic gray whale, Caribbean monk seal • New approaches or technologies increased catch rates docsity.com Several factors mask declines • Industrialized fishing has depleted stocks, global catch has remained stable for the past 20 years – fishing fleets travel longer distances to reach less-fished portions of the ocean – fleets spend more time fishing and have been setting out more nets and lines • increasing effort to catch the same number of fish – improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting docsity.com We are “fishing down the food chain” • Figures on total global catch do not relate the species, age, and size of fish harvested • As fishing increases, the size and age of fish caught decline – 10-year-old cod, once common, are now rare • As species become too rare to fish, fleets target other species – shifting from large, desirable species to smaller, less desirable ones docsity.com Consumer choices influence fishing practices • Buy ecolabeled seafood – Certified sustainable • Consumers don’t know how their seafood was caught – nonprofit organizations have devised guides for consumers – Best choices: farmed catfish and caviar, mussels, oysters, tilapia, sardines, Canadian snow crab – Avoid: Atlantic cod, wild- caught caviar, sharks, farmed salmon docsity.com