Sign up to access the complete lesson and track your progress!
Unlock This CourseCoastal ecosystems are some of the most dynamic environments on Earth, where land meets sea in a constant dance of change. These areas are shaped by non-living (abiotic) factors that create the perfect conditions for unique communities of plants and animals to thrive. Understanding these abiotic characteristics is crucial for protecting and managing our coastal environments.
Key Definitions:
Coastal environments vary dramatically in their physical makeup. Rocky shores provide hard surfaces for attachment, whilst sandy beaches offer loose, shifting substrates. Each structure supports different types of life and creates unique microhabitats.
Temperature is one of the most important abiotic factors affecting coastal ecosystems. Unlike the open ocean, coastal waters experience much greater temperature fluctuations due to their shallow depth and proximity to land.
Coastal waters can experience temperature swings of 10-15°C between day and night and even greater variations between seasons. These changes affect everything from the metabolic rates of marine organisms to the timing of breeding cycles.
Warmer temperatures increase biological activity but can reduce oxygen levels. Many species become more active, whilst others seek cooler, deeper waters.
Cooler temperatures slow down biological processes. Some species migrate to warmer waters, whilst others enter dormant states to survive.
These isolated pools can experience extreme temperature variations, creating challenging conditions that only specially adapted organisms can survive.
The North Sea experiences seasonal temperature ranges from 4°C in winter to 18°C in summer. This variation affects the distribution of species like cod, which prefer cooler waters and sea bass, which thrive in warmer conditions. Climate change is gradually increasing these temperatures, causing shifts in fish populations and affecting coastal ecosystems along the UK's eastern shores.
Salinity levels in coastal waters are constantly changing due to freshwater inputs from rivers, rainfall and evaporation. These variations create unique challenges and opportunities for coastal organisms.
Coastal salinity is influenced by several factors that create a complex mosaic of different salt concentrations. Understanding these patterns helps explain why certain species are found in specific coastal locations.
Rivers, streams and groundwater reduce salinity levels, creating brackish conditions. Estuaries are prime examples where salinity gradually increases from river mouth to open sea.
In shallow coastal areas, especially during hot weather, evaporation can increase salinity above normal seawater levels, creating hypersaline conditions that only specialised organisms can tolerate.
The physical force of waves shapes coastal environments more than almost any other abiotic factor. Wave energy determines what types of organisms can survive and where they can live along the shore.
Different parts of the coast experience varying levels of wave energy, creating distinct zones with unique characteristics and species compositions.
Exposed rocky coasts face powerful waves that prevent sediment accumulation but provide excellent oxygenation. Only organisms with strong attachment mechanisms survive here.
Semi-protected areas with moderate wave action support diverse communities. These areas often have mixed substrates of rock, sand and pebbles.
Sheltered bays and estuaries allow fine sediments to settle, creating mudflats and salt marshes that support different types of organisms.
The Jurassic Coast demonstrates how wave energy varies along a single coastline. At Durdle Door, high-energy waves have carved dramatic limestone arches, supporting communities of barnacles and limpets adapted to strong wave action. In contrast, the sheltered waters of Poole Harbour create low-energy conditions perfect for seagrass beds and wading birds. This 95-mile stretch shows how abiotic factors create diverse coastal habitats within a relatively small area.
Tides create one of the most predictable yet challenging abiotic conditions in coastal ecosystems. The regular rise and fall of water levels creates distinct zones where organisms must cope with alternating periods of submersion and exposure.
The area between high and low tide marks is divided into distinct zones, each with its own abiotic conditions and adapted species. This zonation is one of the clearest examples of how abiotic factors shape ecosystem structure.
Above the high tide mark, this area is only wetted by spray and storm waves. Organisms here must tolerate long periods of drying and high salt concentrations from evaporating seawater.
Exposed only during the lowest tides, this zone remains underwater most of the time. Organisms here are less adapted to drying out but must cope with strong wave action.
The type of material that forms the sea floor and shoreline has a massive impact on coastal ecosystems. Different substrates provide different opportunities for attachment, burrowing and feeding.
Hard rock surfaces provide stable attachment points for many coastal organisms but offer limited space for burrowing species. The type of rock also affects pH levels and nutrient availability.
Hard, resistant granite creates stable platforms but weathers slowly, providing few nutrients. These shores often support communities dominated by barnacles and seaweeds.
Softer limestone weathers more quickly, creating rock pools and crevices. The calcium carbonate also buffers pH levels, supporting shell-forming organisms.
Relatively soft sandstone erodes to create sandy beaches below. These areas often have high sediment loads that affect water clarity and feeding conditions.
Dissolved oxygen levels in coastal waters vary significantly depending on temperature, wave action and biological activity. These variations create different conditions that favour different types of organisms.
Constant wave action ensures high oxygen levels by mixing air into the water. These well-oxygenated conditions support active organisms like fish and mobile invertebrates.
Calm waters with fine sediments often have lower oxygen levels, especially in deeper layers. These conditions favour organisms adapted to low-oxygen environments, such as certain worms and bacteria.
The Thames Estuary demonstrates how human activities can dramatically affect abiotic conditions in coastal ecosystems. Historical pollution reduced oxygen levels so severely that the river was declared biologically dead in the 1950s. Massive cleanup efforts have restored oxygen levels, allowing species like salmon and seals to return. This case shows how abiotic factors can be altered by human activity and how restoration efforts can reverse damage to coastal ecosystems.
Light availability decreases rapidly with depth in coastal waters, especially where sediment loads are high. This affects the distribution of photosynthetic organisms like seaweeds and seagrasses, which form the base of many coastal food webs.
Several abiotic factors work together to determine how much light reaches different parts of coastal ecosystems, directly affecting where photosynthetic organisms can survive and thrive.
Clear water allows light to penetrate deeper, supporting seaweed growth at greater depths. Turbid water limits photosynthesis to shallow areas near the surface.