Threats, Human Benefits, Food Web

What are corals?

Plants or animals?Plants make their own foodAnimals depend on outside

sources for their nutritional requirements

They’re animals!Coral animals take

advantage of both forms of nutrition by hosting plant-like algae (protists) in their tissues.

The majority of the coral’s energy needs are provided by tiny algae called zooxanthellae

Zooxanthellae live inside the coral and produce food using the sun’s energy from carbon dioxide and water

Toxicity Testing LabObjectives

Measure the effect of various toxic materials on zooplankton.

Determine the LD50 (Lethal Dose 50%) for a variety of toxic materials.

Lab cont. Introduction

We handle many materials daily that are toxic. We are often unaware of the degree to which they are toxic. In this laboratory we will look at water solutions of several household materials and determine their toxicity to zooplankton.

Measuring toxicity requires a standard method of comparison. A typical method is to determine the concentration of a toxic material that causes 50% mortality in a population of test animals. This is called an LD50 (Lethal Dose 50%) test of toxicity. For a variety of reasons, different animals respond differently to the same toxin. Some animals may be very sensitive to a toxin, whereas others are relatively resistant to its effects. Because species of animals vary, it is important to understand that what is toxic to zooplankton may not necessarily be toxic to other kinds of animals to the same extent.

Many household items that we deal with on a regular basis are toxic materials, but we don’t usually think of them as being toxic. It should be instructive to examine several such materials to determine their toxicity.

Lab cont. Directions

Obtain 5 petri dishes.Label these dishes as follows:

100% 10% 1% 0.1% 0% (control)

Zooxanthellae (zoo-zan-thel-a)Symbiotic

relationshipClose relationship

between two or more organisms

Mutualism: benefiting both partners

Corals animals and zooxanthellae

Sensitive to high light, variations in the concentrations of salt and especially to high temperatures

Use sunlight for photosynthesis

If sea temperature is too high, zooxanthellae leave, causing the corals to appear brilliant white

What is coral bleaching?Bleaching is

what happens to corals when sea temperatures are too warm for zooxanthellae to live

Zooxanthellae gives coral it’s color, when there is more zooxanthellae, the corals are green/brown

Coral Bleaching

Coral Reef Food WebZooxanthellae provide corals with vital

nutrients produced through photosynthesis

Plant life in the sea is composed of microscopic planktonic algae that comprise the base of the entire marine food chain

The wealth of plant life supports quantities of tiny drifting animals (zooplankton) which feel upon drifting plants, and are ultimately swept across coral reefs

Coral polyps feed on zooplankton suspended in the flow of sea water

Zooplankton is a substantial part of the coral reef food chain

Major threats to coral reefsNaturalHurricanesTyphoonsEl NinoCoral-eating

organismsDiseases Ocean

Acidification

HumanOver-fishingCoastal

developmentSewage and

other pollutionRising global

temperaturesCarless tourism

Over-fishingFishing selectively takes larger, predatory fish off

the reef causing explosions of smaller herbivorous fish

When larger fish become scarce, the herbivorous fish are then targeted by fishermen

Without herbivores, seaweeds can overgrow the corals and smother them

Destructive fishing practices include using cyanide to stun fish for capture for the marine aquarium and live fish trades and blast fishing to kill fish for food

Fishing methods are not species-specific, so many organisms are killed in the process and habitats that took thousands of years to build are destroyed

Let’s check the zooplankton!

Coastal DevelopmentCoastal construction often

removes mangroves and seagrass beds, which takes away the sediment barrier

Excess sediments cover corals, blocking light necessary for their symbiotic zooxanthellae

Under natural conditions, corals are able to out-compete seaweeds because of the low nutrient content in tropical waters

When outside nutrients are added, faster growing seaweeds can take over and smother corals

Sewage and other pollutionAdds unnatural and potentially harmful

substances to the reef systems including nutrients, pathogens and trash

Implicated in the apparent surge in coral diseases, especially in the Caribbean

Garbage pollution Sewage pollution

Air pollution

Rising global temperaturesOne of the most global

threats to coral reef ecosystems

What causes global temperatures to rise?Burning of fossil fuelsChanges in land useReduction in forest cover

Why Care about Coral Reefs?Healthy Coral Reefs = A Healthy World

Support 25% of all marine life Provide habitat, income, food, protection, medicine

Animals that live nowhere else Home to more than 4,000 species of fish, 700 species of

coral and thousands of other plant and animal life. Scientists estimate that, in total, more than one million

species of plants and animals are associated with coral reef ecosystems

Millions of humans depend on coral reefs Coral reefs provide economic goods and ecosystem

services worth about $375 billion each yearCoral reefs protect the beaches

Protect 109 countries’ coastlines

Coral reefs save livesSeveral important drugs

have already been developed from chemicals found in coral reef organisms Cardiovascular disease Ulcers Leukemia Skin cancer More than half of all new

cancer drug research focus on marine organisms

Global Climate Change and Our Life Styles

How to reduce greenhouse gas emissions:1. Conserve energy2. Buy a fuel-efficient car and drive less often3. Reduce, re-use and recycle4. Plant trees5. Reduce water use6. Choose sustainable seafood7. Educate yourself!

Get the Facts!Coral reefs are in crisis, dying at an alarming

rate worldwideAn estimated 25% of coral reefs already

disappeared and an estimated two-thirds of all oral reefs are at risk today

An estimated 88% of the reefs in Southeast Asia, the most species rich reefs on earth, are at risk

Since 1975, more than 90% of the reefs in the Florida Keys have lost their living coral cover

The most important fact:There are solutions to this crisis.

Let’s check them again!

Questions?