Comprehensive Study Notes on Marine Ecological Factors and Biology

Ecological Factors of Marine Environments

  • Salinity (Salinitet)

    • Salinity is defined as the total amount of salt contained in 1 kg1\,kg of water.

    • Measurement: It is measured in promilles (parts per thousand).

    • Specific Data: The average salinity of the Adriatic Sea (Jadran) is recorded at 35\,\text{\textperthousand}.

  • Temperature

    • The temperature of the water is primarily dependent on the air temperature.

    • Variable Layers: Changes in temperature most frequently affect the surface layer of the water and the immediate coastal zones.

    • Deep Water Stability: At the sea bottom, the temperature remains constant, ranging between 4 ∘C4\,^{\circ}C and 10 ∘C10\,^{\circ}C.

Light Penetration and Depth Zonation

  • Light (Svjetlost) Dynamics

    • Light penetrates the water to a maximum depth of approximately 200 m200\,m.

    • Production Zone: The highest concentration of biological producers live within the first 50 m50\,m of depth, identifying this as the primary zone of production.

  • Hierarchical Marine Zones

    • The marine environment is divided into four distinct zones based on light availability:

      1. Zone of Light (Zona svjetla): Extends from the surface down to a depth of 200 m200\,m.

      2. Twilight Zone (Zona sumraka): Occupies the depths between 200 m200\,m and 1000 m1000\,m .

      3. Dark Zone (Zona tame): Occupies the depths between 1000 m1000\,m and 4000 m4000\,m.

      4. Abyssal Zone (Zona bezdana): Defined as the region located below 4000 m4000\,m of depth.

Physical Properties and Hydrodynamics

  • Pressure and Density

    • Both pressure and density are higher in marine environments compared to any other water types.

    • Consequence: This increased density results in a greater buoyancy force (sila potiska\text{sila potiska}) acting upon organisms and objects.

  • Water Movement (Kretanje vode)

    • Marine water movement occurs in three primary forms:

      1. Waves (Talasi/Valovi).

      2. Marine Currents (Morske struje): These are directed movements of water that occur when water masses of different temperatures and densities mix, influenced also by the Earth's rotation.

      3. Tides (Plima i Oseka):

        • High Tide (Plima): The rising of the sea level.

        • Low Tide (Oseka): The lowering of the sea level.

        • Causes: Tides are generated by the gravitational pull exerted by the Sun and the Moon.

        • Frequency: This cycle occurs twice within a 24 h24\,h period.

        • Adriatic Context: The average difference between high and low tide in the Adriatic Sea is 60 cm60\,cm.

Marine Biotopes and Sea Floor Composition

  • Coastal Biotope (Obalsko podrucije)

    • This includes the Shore Zone (Priobalska zona), the Splash Zone (Zona prskanja vode), and the Intertidal Zone (Plima i oseka).

  • Benthic Environment (Dna)

    • The sea floor is categorized according to the light zones previously mentioned: the light floor, twilight floor, dark floor, and abyssal floor.

    • Substrate Types: The physical composition of the bottom (dno) can vary and may be:

      • Gravelly (Sljunkovito)

      • Sandy (Pjeskovito)

      • Rocky (Kamenito)

      • Muddy (Muljevito)

Biological Classification of Marine Organisms

  • Marine Organisms (Organizmi mora)

    • Life in the sea is classified into major ecological groups:

      • Nekton: Organisms that can swim actively against water currents.

      • Plankton: Organisms that drift or float in the water.

        • Phytoplankton (Fitoplankton): The plant-like, photosynthetic component of plankton.

        • Zooplankton: The animal-like component of plankton.