Marine Biology

🐠Marine Biology Unit 11 – Coastal and Intertidal Ecology

Coastal and intertidal zones are dynamic areas where land meets sea, characterized by unique physical and biological processes. These regions experience constant changes due to tides, waves, and environmental factors, creating diverse habitats from rocky shores to mudflats. Intertidal organisms have adapted to survive extreme conditions, including desiccation, temperature fluctuations, and salinity changes. The interplay of physical factors and biological interactions shapes distinct zonation patterns, influencing biodiversity and ecosystem dynamics in these fascinating transitional environments.

Key Concepts and Terminology

  • Intertidal zone the area between the high and low tide lines on a shoreline
    • Divided into three subzones: high, middle, and low intertidal zones based on the duration of exposure to air and water
  • Zonation the distribution of organisms in distinct horizontal bands along the intertidal zone determined by physical factors and biological interactions
  • Tides the rise and fall of sea levels caused by the gravitational pull of the moon and sun
    • Spring tides occur during full and new moons when the tidal range is greatest
    • Neap tides occur during the first and third quarter moons when the tidal range is smallest
  • Emersion the period when the intertidal zone is exposed to air during low tide
  • Immersion the period when the intertidal zone is submerged in water during high tide
  • Desiccation the process of drying out or dehydration experienced by intertidal organisms during emersion
  • Osmotic stress the physiological challenge faced by intertidal organisms due to changes in salinity during tidal cycles
  • Keystone species a species that has a disproportionately large effect on the ecosystem relative to its abundance (sea otters, sea stars)

Coastal and Intertidal Zones Overview

  • Coastal zones are dynamic interfaces between land and sea characterized by unique physical, chemical, and biological processes
  • Intertidal zones are transitional areas between the land and sea that are alternately exposed to air and submerged in water due to tidal cycles
  • Intertidal habitats include rocky shores, sandy beaches, mudflats, and salt marshes each with distinct characteristics and ecological communities
  • Vertical zonation patterns in the intertidal zone are determined by the interplay of physical factors (tides, wave action, temperature, salinity) and biological interactions (competition, predation, facilitation)
    • Upper intertidal zone is exposed to air for the longest duration and experiences the greatest temperature and salinity fluctuations
    • Middle intertidal zone is exposed to air and submerged in water for roughly equal durations and hosts a diverse array of organisms
    • Lower intertidal zone is submerged in water for the longest duration and experiences the least environmental stress
  • Horizontal zonation patterns along the shoreline are influenced by factors such as wave exposure, substrate type, and freshwater input
  • Intertidal organisms exhibit various adaptations to cope with the challenges of living in a constantly changing environment (desiccation resistance, osmotic regulation, adhesion mechanisms)

Physical Factors and Adaptations

  • Tidal cycles are the primary physical factor shaping intertidal ecosystems exposing organisms to alternating periods of emersion and immersion
  • Wave action influences the distribution and morphology of intertidal organisms
    • High wave exposure can cause physical damage and dislodgement of organisms
    • Low wave exposure allows for the accumulation of sediments and the establishment of soft-bottom communities
  • Temperature fluctuations in the intertidal zone can be extreme during emersion with organisms experiencing both heat stress and cold stress
    • Organisms adapt by seeking shelter in crevices, under rocks, or by aggregating to reduce water loss and maintain body temperature
  • Salinity changes occur due to evaporation during emersion and freshwater input from rivers or rainfall
    • Intertidal organisms regulate their osmotic balance through various mechanisms (osmoconformers, osmoregulators)
  • Desiccation is a major challenge for intertidal organisms during emersion
    • Adaptations to reduce water loss include impermeable exoskeletons, mucus secretion, and the ability to trap water in shell valves (mussels, barnacles)
  • Substrate type (rocky, sandy, muddy) influences the attachment and burrowing abilities of intertidal organisms
    • Rocky shores provide stable attachment sites for sessile organisms (barnacles, mussels, seaweeds)
    • Sandy and muddy substrates are inhabited by burrowing organisms (clams, worms, crustaceans)

Biodiversity and Ecosystem Dynamics

  • Intertidal zones host a diverse array of marine organisms including algae, invertebrates, and vertebrates
  • Biodiversity patterns in the intertidal zone are influenced by physical gradients, biological interactions, and larval dispersal
  • Competitive interactions among intertidal organisms can lead to the exclusion of inferior competitors and the formation of distinct zonation patterns
    • Competition for space is intense in the intertidal zone, with sessile organisms often overgrowing or displacing each other
  • Predation plays a significant role in structuring intertidal communities
    • Keystone predators (sea stars) can control the abundance and distribution of their prey (mussels), maintaining species diversity
  • Facilitative interactions, such as the provision of habitat or protection by one species to another, can enhance local biodiversity
    • Mussel beds provide shelter and attachment sites for various invertebrates and algae
  • Trophic relationships in intertidal food webs are complex and involve multiple pathways of energy transfer
    • Primary producers (algae) form the base of the food web, supporting a variety of herbivores and detritivores
    • Carnivores (sea stars, crabs, fish) feed on herbivores and other carnivores, regulating their populations
  • Ecosystem engineers, such as reef-building organisms (oysters, corals) and seagrasses, create complex habitats that support diverse ecological communities

Human Impacts and Conservation

  • Coastal development, such as the construction of seawalls, jetties, and marinas, can alter intertidal habitats and disrupt natural processes
    • Hardening of shorelines can lead to the loss of sandy beaches and the associated biodiversity
  • Pollution from land-based sources (agricultural runoff, sewage discharge, industrial waste) can degrade water quality and harm intertidal organisms
    • Eutrophication caused by excess nutrients can lead to algal blooms and hypoxic conditions
  • Overharvesting of intertidal resources (shellfish, seaweeds) can disrupt food webs and reduce population resilience
    • Unsustainable fishing practices, such as bottom trawling, can damage intertidal habitats and non-target species
  • Climate change impacts, including sea-level rise, ocean acidification, and increased storm intensity, pose significant threats to intertidal ecosystems
    • Rising sea levels can lead to the submergence and loss of intertidal habitats, particularly in areas with limited room for landward migration
    • Ocean acidification can impair the growth and survival of calcifying organisms (mollusks, crustaceans)
  • Marine protected areas (MPAs) are an effective tool for conserving intertidal biodiversity and promoting sustainable resource use
    • No-take reserves, where extractive activities are prohibited, can allow for the recovery of overexploited populations and the restoration of ecosystem functions
  • Coastal habitat restoration projects, such as the reestablishment of salt marshes or the removal of invasive species, can enhance the resilience of intertidal ecosystems
  • Public outreach and education programs can raise awareness about the importance of intertidal zones and promote responsible human behaviors

Research Methods and Field Techniques

  • Quadrat sampling involves the use of a square frame to quantify the abundance and distribution of intertidal organisms within a defined area
    • Quadrats can be randomly placed or arranged along transects to capture spatial patterns
  • Transect surveys are used to assess changes in species composition and zonation patterns across environmental gradients
    • Vertical transects run perpendicular to the shoreline, from the upper to the lower intertidal zone
    • Horizontal transects run parallel to the shoreline, capturing variations in wave exposure or substrate type
  • Biomass estimation techniques, such as dry weight or ash-free dry weight, are used to quantify the productivity and standing stock of intertidal organisms
  • Mark-recapture studies are employed to estimate population sizes, growth rates, and movement patterns of mobile intertidal organisms (crabs, snails)
    • Individuals are marked with tags or paint and released, then subsequently recaptured to calculate population parameters
  • Remote sensing techniques, such as aerial photography and satellite imagery, can provide broad-scale information on intertidal habitat distribution and change over time
  • Physiological measurements, such as respiration rates, thermal tolerance limits, and osmotic regulation capacity, are used to assess the adaptations and stress responses of intertidal organisms
  • Stable isotope analysis can reveal trophic relationships and energy flow pathways within intertidal food webs
    • The ratios of carbon and nitrogen isotopes in tissues can indicate the primary sources of nutrition for consumers
  • Manipulative experiments, such as exclusion cages or transplantation studies, are used to test hypotheses about the roles of biotic and abiotic factors in shaping intertidal communities
    • Exclusion cages can selectively remove predators or competitors to examine their effects on community structure
    • Transplantation studies involve moving organisms to different zones or habitats to assess their responses to new conditions

Case Studies and Real-World Applications

  • The Monterey Bay National Marine Sanctuary in California encompasses a diverse array of intertidal habitats, from rocky shores to sandy beaches
    • Research in the sanctuary has revealed the importance of keystone predators, such as sea otters, in maintaining kelp forest ecosystems and intertidal community structure
  • The Wadden Sea, a large intertidal zone along the coasts of the Netherlands, Germany, and Denmark, is a critical stopover site for migratory birds
    • Conservation efforts in the Wadden Sea focus on protecting intertidal mudflats and seagrass beds, which provide food and shelter for millions of shorebirds
  • The Great Barrier Reef in Australia includes extensive intertidal habitats, such as mangrove forests and coral reefs
    • Climate change impacts, including coral bleaching and sea-level rise, pose significant threats to the intertidal communities of the Great Barrier Reef
  • The Gulf of Maine in the northwestern Atlantic Ocean experiences extreme tidal ranges, creating expansive intertidal zones
    • Studies in the Gulf of Maine have investigated the effects of invasive species, such as the European green crab, on native intertidal communities
  • The Galapagos Islands in the eastern Pacific Ocean are renowned for their unique intertidal fauna, including marine iguanas and Sally Lightfoot crabs
    • Research in the Galapagos has provided insights into the adaptations of intertidal organisms to extreme environmental conditions, such as high temperatures and low nutrient availability
  • The Banc d'Arguin National Park in Mauritania is a vast intertidal zone that supports the largest concentration of wintering shorebirds in the world
    • Conservation measures in the park aim to protect the intertidal seagrass beds and mudflats that are essential for the survival of migratory birds
  • The Bay of Fundy in eastern Canada is known for its record-breaking tidal ranges, which can exceed 16 meters
    • Studies in the Bay of Fundy have investigated the ecological consequences of tidal energy extraction on intertidal communities

Review and Discussion Points

  • What are the key physical factors that shape intertidal ecosystems, and how do organisms adapt to these challenges?
  • How do biotic interactions, such as competition, predation, and facilitation, influence the structure and diversity of intertidal communities?
  • What are the major human impacts on intertidal zones, and what conservation strategies can be employed to mitigate these threats?
  • How do research methods and field techniques differ between rocky shores, sandy beaches, and soft-bottom habitats in the intertidal zone?
  • What can case studies from around the world teach us about the ecological importance and vulnerability of intertidal ecosystems?
  • How might climate change impacts, such as sea-level rise and ocean acidification, alter the distribution and composition of intertidal communities in the future?
  • What are the economic and cultural values of intertidal resources, and how can these be balanced with conservation goals?
  • How can citizen science and public participation contribute to the monitoring and management of intertidal zones?


© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.