Coastal Transitional Environments – Quick Reference

Coastal zones that are low-lying, with sandy or muddy substrates (not primarily rocky cliffs); include salt marshes in higher latitudes.
Transitional between freshwater and saltwater; salinity is a key abiotic gradient shaping habitat structure.
Salinity can stratify water columns, creating zones accessible to organisms with different salt tolerances (amphibians sensitive to salt; reptiles like snakes and alligators more tolerant).

Salinity stratification defines habitat compartments and species distributions.
Amphibians generally not tolerant of saltwater; some vertebrates (e.g., many reptiles) tolerate or thrive in brackish conditions.

Oxygen concentration is crucial: more oxygen = healthier populations and faster growth.
Salinity and other factors can create extremes in oxygen levels.

Salt marshes contain a network of tidal channels and pools, bordered by natural levees and basins.
Predominantly muddy, with limited hard substrate; flow is driven by tides.
Channel width varies; some systems have multiple small streams, others a main river-like channel.

Plants occupy zones based on inundation depth; deeper areas may be fully submerged with little to no vegetation.
Shallower areas heat up more due to sun exposure; deeper, low-lying areas stay cooler.

Tropical woody trees with exposed, intricate root systems; roots reach into the water and provide structure.
Roots/branches form a tangled habitat that protects against storm surge and provides nursery habitat for fish and other marine life.
Distribution follows the intertidal height gradient from water to inland; inland spread depends on competition from dune species or taller trees.
Seeds drop from branches, float, and take root in suitable habitat.

Dense roots trap substrate and debris, stabilizing shorelines and reducing erosion.
Provide critical nursery habitat, especially for young fish.
Coastal protection: mangroves buffer storms and surge.
Economic/value example (Florida): mangroves protected shorelines and reduced damages; $1.5 imes 10^9$ dollars in indirect flood damages prevented over the coming century; global ecosystem services valued near $10^{12}$ dollars in today’s money.

Deforestation for fuel and wood, aquaculture and agriculture, urban development.
Erosion and habitat loss; pollution (nutrient runoff) contributing to hypoxia and algal blooms.
Jubilee events: nutrient-rich runoff (e.g., Mississippi drainage) drives large fish kills as nutrients flood coastal waters.

Fisheries observers monitor bycatch (non-target species such as sea turtles, invertebrates, and sometimes marine mammals).
Bycatch data are used by agencies like NOAA to assess population health; some practices involve testing captured animals for diseases (e.g., nasal testing).

Pelagic trawl: open-ocean targeting; some bycatch but lower habitat contact than bottom trawls; higher fuel use and entanglement risk.
Benthic (bottom) trawl: targets bottom-dwelling species; heavy habitat destruction and high bycatch potential; high fuel use.
Longline: high species selectivity (specific targeted species) with low habitat impact, but bycatch of sea turtles, seabirds, and sharks is a concern; long lines carry thousands of hooks.

Structures like oil rigs can attract wildlife and function as artificial reefs, providing habitat complexity.
Wind-turbine sonar testing nearshore has raised concerns about whale disruption; evidence of impact is not statistically conclusive.
Oil rigs historically used sonar techniques to map the seafloor; ongoing debates about balancing energy development with marine life protection.

Tundra in Alaska: little to no trees due to cold temperatures and elevation.
Notable species discussed: Pacific halibut (large flatfish; two eyes on one side; eye migration during development).
Common coastal birds: great black-backed gulls with broad ranges (migrate or reside seasonally).
Pollock variant: melanistic individual (melanistic mutation) observed among some species often used in fish products.

Pacific halibut: enormous flatfish with eye migration; important deep-water/groundfish species.
Great black-backed gull: wide geographic range along coasts.
Pollock (melanistic variant): bright red-toned individual with reduced melanin.
Seabird/fish interactions: seabirds often associate with coastal structures or fish schools; sea turtles may be observed in nearshore habitats.