Kelp Forests Summary

Kelp Forests Overview

  • Kelp forests are prominent along the West and South West coasts of Southern Africa.
  • Key Species:
    • Sea Bamboo (Ecklonia maxima) - largest and most common.
    • Split Fan Kelp (Laminaria pallida).

Characteristics of Kelp Forests

  • Kelp requires rocky surfaces to grow due to strong wave action.
  • Found from the infratidal zone to 3 km offshore in waters shallower than 30 m.
  • Kelp ecosystems are comparable to tropical forests in biodiversity.
  • Thrive in nutrient-rich waters due to upwelling from gales.

Kelp Forest Zonation

  • Inshore Zone:

    • Depth: 1-2 m
    • Features: Smaller sea bamboo and abundant benthic algae. Low abundance of larger animals.

  • Intermediate Zone:

    • Depth: <15 m
    • Features: Dense stands of sea bamboo with Split fan kelp forming understorey. Low animal diversity, mainly invertebrates and filter feeders.

  • Offshore Zone:

    • Features: Island-like stands of Split fan kelp with more open reef sections. High abundance of herbivores and filter feeders in calmer areas.

Kelp Forest Productivity

  • Highly productive ecosystems; exceed agricultural productivity per area.
  • Kelp grows continuously, with fronds softening and breaking off due to turbulence.
  • Decomposed kelp provides nutrients and promotes phytoplankton blooms after upwelling events.

Ecological Significance

  • Kelp forests reduce wave action and provide shelter for diverse marine life.
  • Nutrients from kelp decomposition support herbivores and filter feeders.
  • Organisms include:
    • Producers: Kelp, phytoplankton.
    • Herbivores: Sea Urchins, limpets, sea cucumbers, mussels.
    • Carnivores: Lobsters, reef sharks, seals, otters.

Food Web Dynamics

  • Complexity in the food web: interdependence among producers, primary consumers, and predators.
  • Limited herbivory on living kelp, with some specialized species (e.g., Kelp limpet) protecting kelp from overgrazing.