4.1 Marine Ecosystems
Marine ecosystems encompass the incredible diversity of life in the ocean, from microscopic bacteria to great whales. Understanding their structure, function, and interconnections is fundamental to biological oceanography.
Ocean Zones
Epipelagic (0-200m)
Sunlit zone. Photosynthesis occurs. Most primary production. Rich biodiversity.
Mesopelagic (200-1000m)
Twilight zone. Dim light. Diel vertical migration. Bioluminescence common.
Bathypelagic (1000-4000m)
Midnight zone. No light. Cold (~4°C). High pressure. Sparse life.
Abyssopelagic (4000-6000m)
Abyssal zone. Near-freezing. Extreme pressure. Specialized fauna.
Ecosystem Types
Coral Reefs
25% of marine species. Tropical. Built by cnidarians. Threatened by warming.
Kelp Forests
Temperate coasts. Macroalgae create 3D habitat. High productivity.
Mangroves
Coastal nurseries. Salt-tolerant trees. Carbon storage. Storm protection.
Open Ocean
Pelagic ecosystem. 70% of ocean. Lower productivity but vast area.
Python: Biomass Distribution
#!/usr/bin/env python3
"""marine_ecosystems.py - Ocean biomass by trophic level"""
import numpy as np
import matplotlib.pyplot as plt
# Approximate marine biomass (Gt C)
trophic_levels = ['Bacteria', 'Phytoplankton', 'Zooplankton',
'Fish/Invertebrates', 'Marine Mammals']
biomass = [1.2, 3.0, 0.7, 0.8, 0.01] # Gt C
plt.figure(figsize=(10, 6))
colors = ['#8B4513', '#228B22', '#4169E1', '#FF6347', '#9370DB']
plt.barh(trophic_levels, biomass, color=colors)
plt.xlabel('Biomass (Gt C)')
plt.title('Marine Biomass by Category')
plt.xscale('log')
for i, v in enumerate(biomass):
plt.text(v*1.2, i, f'{v} Gt C', va='center')
plt.tight_layout()
# Trophic efficiency calculation
primary_production = 50 # Gt C/year
efficiency = 0.1 # 10% transfer efficiency
secondary = primary_production * efficiency
tertiary = secondary * efficiency
print(f"Primary production: {primary_production} Gt C/yr")
print(f"Secondary production: {secondary} Gt C/yr")
print(f"Tertiary production: {tertiary} Gt C/yr")