Functional and Behavioural Adaptations to Living in Marine Environments

Main Themes:
- Organismal Adaptations
- Physical and Ecological Factors
- Aerial Exposure, Temperature, and Desiccation
- Gas Exchange, Predation/Herbivory, Pressure
- Locomotion/Buoyancy, Competition, Wave Exposure
- Feeding, Larval Supply and Recruitment
- Salinity, Reproduction and Development
- Facilitation, Sediments, Position Maintenance, Bioturbation
- Behavioural Rhythms and Orientation
- Communication, Disturbance, Deep Water Adaptation
- Top-Down/Bottom-Up Processes, Light
- Note: Gas exchange covers marine organisms beyond just aerial exposure adaptations

Tidal Cycles: Approximately 12.4 hours
Diurnal Cycles: Approximately 24 hours
Semilunar Cycles: Approximately 28 days
Seasonal Cycles: 365 days
Impact of Geophysical Events:
- Dictate aerial exposure's duration and extent for intertidal organisms, especially sessile species
Temperature Ranges on Exposed Shores:
- Can vary from well below freezing to above 35°C
- Daily temperature fluctuations may exceed 20°C in specific locations
- Example: Modiolus demissus tolerates temperatures from -22°C to +40°C

Abiotic Stresses:
- Intertidal organisms face various stresses including:
- Aerial exposure
- Extreme temperature variations
Thermal Tolerance Differences:
- Intertidal species generally exhibit higher thermal tolerance limits compared to subtidal species
- Tropical species show higher tolerance than temperate species (e.g., Petrolisthes violaceous)

Mortality Due to Thermal Stress:
- Can lead to direct mortality from extreme temperatures
- Increased susceptibility to predation under thermal stress
- Sublethal thermal stress can decrease fitness due to physiological costs of repair and protection for cells

Challenges of High Temperatures:
- Generally more problematic than low temperatures
- Effects include:
- Protein denaturation affecting cell processes and integrity
- Disruption of membrane functions, including ciliary action
- Q10 rule indicating enzyme reaction rates increase with temperature until denaturation occurs
- Desiccation and ionic imbalance

Homeotherms:
- Mainly include mammals and birds, maintaining constant body temperature (Tb)
Ectotherms:
- Include invertebrates, most fish, and plants; ambient temperature affects metabolic rates (Mr) and behaviour

Morphological Adaptations:
- High-shore animals often larger relative to those lower on shore to minimize surface area to volume ratio, reducing heat gain
- Example: Larger Littorina littorea found higher on the shore
- Some snails attach to overhangs via mucus threads to reduce substrate contact (only on low energy shores)

Air-Cooled Organisms:
- Ridges in the shells of gastropods serve as radiators to dissipate heat (e.g., Tectarius muricata)
Heat Retention by Color:
- Darker organisms gain/lose heat faster than lighter ones
- Lighter shells keep cooler for longer; tropical snails typically have lighter shells compared to temperate ones

Evaporative Heat Loss:
- While effective, it risks desiccation
- Some organisms, such as Tetraclita rubescens (barnacle), have thick shells to trap water which evaporates during low tide

Hiding and Grouping:
- Intertidal organisms like Collisella digitalis (fingernail limpet) utilize crevices to conserve moisture and avoid heating
Empirical Evidence for Crevices:
- Helcion pectunculus shows that crevice refuges significantly reduce heating

Phototaxis Changes in Afruca tangeri:
- Exhibits different directional behaviour at different times of the day; positive at dawn and dusk, negative during peak heat times

Challenges for Intertidal Animals:
- Highly variable environments, pronounced for sessile rocky shore organisms
- Aerial exposure leads to thermal stress and desiccation
- Adaptation strategies include morphological, behavioural, and physiological mechanisms

Heat Shock Factors:
- When exposed to heat stress, proteins called heat shock factors dissociate from carriers, activating heat shock genes which produce heat shock proteins (HSPs)
Function of HSPs:
- Serve as molecular chaperones, preventing protein damage, refolding damaged proteins, and maintaining membrane functionality

Study of Snails Tegula rugosa:
- Found along intertidal regions with temperatures up to 40°C in Gulf of Mexico versus subtidal and low-mid intertidal species

HSP70 and Shore Position Correlation:
- Reflected the survivorship patterns observed with temperature variations between intertidal and subtidal species

Notable Exemption - Trematomus bernacchii:
- Antarctic ice fish that inhabits a stable temperature environment and lacks the heat-shock response mechanism

Example of Pompeii Worm (Alvinella pompejana):
- Polychaete found in black smoker walls at depths over 2000m, withstands extreme temperatures
- Tolerance range: 22°C to 80°C from hole aperture to the hole end, indicating significant eurythermal adaptability

Experimental Findings on % Animal Survival:
- Data illustrated survival rates across various sampling temperatures (20°C, 42°C, and 55°C) with varying Hsp70 normalized expression rates