🐠Marine Biology Unit 11 – Coastal and Intertidal Ecology

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?