Comprehensive IGCSE Marine Science Study Notes (0697)

Chapter 6.1: Overview of Human Interactions with Marine Ecosystems

Hello Marine Scientists! This chapter is all about the relationship between humans and the amazing ocean environment. We will look at how much we rely on marine ecosystems, and unfortunately, the ways our actions are causing harm. Understanding these interactions is the first crucial step towards finding solutions!

Section 1: Why Marine Ecosystems are Important to Us (6.1.1)

The ocean is not just beautiful; it is essential for human survival, culture, and economy. Here is a breakdown of the key ways we use marine ecosystems:

1. Food Supply and Fisheries

Food supply is arguably the most obvious importance. We rely on the ocean for fish, shellfish, and macroalgae (seaweed) which provide essential nutrients and protein globally. The business of catching these organisms is called fisheries.

2. Economic and Recreational Value

  • Recreation and Tourism: Activities like diving, snorkeling, sailing, and beach holidays generate massive amounts of income and provide employment for coastal communities.
  • Example: A thriving coral reef attracts thousands of tourists, supporting local hotels and boat operators.

3. Coastal Protection

Certain ecosystems act as natural barriers against storms, waves, and erosion:

  • Coastal Protection: Ecosystems like mangrove forests (with their dense, tangled roots) and coral reefs absorb wave energy, protecting coastal land and infrastructure from damage.
  • Did you know? Mangroves can reduce the height of storm surges, acting like a giant sponge!

4. Resources and Materials

  • Source of Wood/Building Material: Mangrove wood is sometimes used for construction or fuel. Sand and mud are often dredged from coastal areas (though this causes severe environmental impact) to be used as building materials for land reclamation.
  • Medicines and Medicinal Plants: Many marine organisms (like sponges, sea squirts, and microalgae) contain unique compounds used to develop new drugs to treat diseases, including cancer.

5. Supporting New Life (Nursery Areas)

Certain shallow, protected habitats are vital for the survival of many species:

  • Nursery Areas: Habitats like mangrove forests and seagrass beds provide safe, food-rich areas for the juveniles (young) of commercially and ecologically important species (e.g., small fish, shrimp, crabs) before they move to the open ocean or reef.

Quick Takeaway: Humans rely on marine ecosystems for food, income (tourism), natural defense (coastal protection), and new resources (medicines).

Section 2: The Negative Impacts of Human Activities (6.1.2)

Unfortunately, our demand for resources and our presence in coastal areas often leads to serious negative impacts on the marine environment. Don't worry if this list seems long; we can group the impacts into categories!

1. Physical Disturbance and Pollution from Recreation

When tourists and locals visit marine environments, several problems arise:

  • Noise and Light Pollution: This can disrupt breeding cycles, feeding, and migration patterns of animals (like turtles or cetaceans).
  • Litter and Plastics: Garbage, especially plastics, can kill marine life through ingestion (eating it) or entanglement.
  • Trampling of Organisms: People walking or standing on fragile habitats, such as coral reefs or rock pools, causing direct damage.
  • Collection and Removal of Organisms as Souvenirs: Taking shells, corals, or small animals reduces species populations and disrupts the ecosystem.
  • Tourist Boats and Diving: Boats can leak fuel and anchor carelessly, smashing fragile coral. Divers, if poorly trained, can also kick or touch organisms.

2. Habitat Destruction for Infrastructure

The development of coastal areas for human use often requires destroying natural habitats:

  • Land Reclamation for Resorts: Filling in coastal wetlands or shallow areas to create new land for resorts or housing destroys crucial nursery habitats (like mangroves).
  • Building of Infrastructure: Construction of jetties, ports, and sea walls permanently changes the coastline and disrupts natural processes.
  • Removal of Resources: Dredging (scooping up sand/mud) for building materials destroys the seafloor habitats where benthic organisms live. Logging of mangrove trees removes coastal protection and nursery areas.

3. Destructive Fishing and Farming

  • Blast Fishing: An illegal method where explosives are used to stun or kill fish, indiscriminately destroying surrounding habitats like coral reefs. It’s destructive because it kills everything, not just the target fish.
  • Shrimp Farms: Often built by clearing mangrove forests (habitat loss). The farms themselves can cause local pollution due to waste products and chemicals.

4. Oil Spills

  • Oil Spills: These catastrophic events occur during oil extraction or transportation (see Chapter 6.5). The oil floats on the surface, cutting off light and oxygen, and poisons animals.

Quick Takeaway: Human impacts range from direct physical damage (trampling, blast fishing) to habitat loss (reclamation, mangrove logging) and various forms of pollution (plastics, oil).

Section 3: Species Decline and Sustainability (6.1.3 & 6.1.4)

1. Endangered Species (6.1.3)

What happens when populations decline?

Human activities, especially overfishing, pollution, and habitat loss, cause the populations of many marine species to drop.

  • If a population declines too rapidly, it struggles to reproduce fast enough to recover.
  • When a species faces a very high risk of extinction (dying out completely) in the wild, it is classified as an endangered species.
  • Example: Many species of marine turtles and whales are endangered due to historic hunting, habitat loss, and accidental entanglement in fishing gear.

2. The Need for Sustainable Practices (6.1.4)

What is Sustainability?

We need to be able to use the ocean's resources without destroying the environment for future generations. This is the core concept of sustainability.

A sustainable resource or activity is one that we can continue to use or carry out at the current rate, without:

  1. Causing long-term damage to the environment.
  2. Causing the resource to run out.

Analogy: If you have a chocolate bar (the resource) and you want it to last forever (sustainability), you can only nibble a tiny amount each day without letting it disappear. If you eat half of it now (unsustainable), it will eventually run out.

Key Takeaway: Unsustainable human activities lead to declining populations and endangered species. We must switch to sustainable practices that allow us to use resources without damaging the ecosystem or running out.