Sandy & Rocky Beach Ecosystems: A Comprehensive Study
Sandy beach communities generally have uniform topography. Wave action, sunlight, and dryness affect the beach uniformly, and life depends mainly on tidal amplitude. Dead organisms are common; birds, rodents, and insects are often observed, along with microalgae.
Coastal System or Phytalidae
Supralittoral Zone: The dominant species is the carter (please specify the full scientific name).
Mesolitoral Zone: Dominant species include Emerita analoga, along with mollusks, crustaceans, polychaetes, and fish.
Sandy beach communities occupy large areas, providing abundant food. The organic surface film supports burrowing organisms. In Peru, these communities are generally located in the north and areas adjacent to mangrove areas.
Common organisms include mollusks, crustaceans, echinoderms, polychaetes, and fish.
Aquatic Life:
Definition: A set of complex adaptations and structural behaviors that contribute to a species’ self-preservation in its natural environment.
Types of Relationships with Lifestyles:
- Substrate use for food, locomotion, resistance, and reproduction.
Relationship with the Terrain:
- Epibiosis: Organisms living on a substrate (epifauna):
- Sessile: Organisms with fixed bodies, such as macroscopic algae (excluding Sargassum).
- Motile: Organisms with varying degrees of movement:
- Pivot: Organisms rooted on a mobile surface (e.g., anemones, sponges).
- Sedentary: Organisms with small-amplitude movement (e.g., gastropods, some anemones).
- Vagile: Organisms with broad movement (e.g., crustaceans, cephalopods, fish).
- Endobiosis: Organisms that burrow into the substrate (infauna):
- Digger: Organisms that burrow into soft substrates (e.g., sandy or muddy substrates; scaphopods, bivalves).
- Borer: Organisms that bore into hard substrates (e.g., wood or rock; some bivalves, annelids, sponges).
Obtaining Food:
Organisms may be autotrophic or heterotrophic (carnivores, piscivores, insectivores, herbivores, parasites). Other methods include grazing, filter feeding, and hunting/trapping.
Locomotion:
Locomotion and sensitivity in a homogeneous medium include crawling, drilling, digging, floating, swimming, and gliding.
Mollusks:
Mollusks are benthic, marine, freshwater, or terrestrial animals with bilateral symmetry, soft bodies, and often a shell. They are classified into seven groups:
- Aplacophora: Vermiform, shell-less mollusks with a rudimentary foot (e.g., Neomenia).
- Monoplacophora: Mollusks with a single, conical shell (e.g., Neopilina).
- Polyplacophora (chitons): Mollusks with eight overlapping shell plates.
Movement of Water:
Waves, tides, and currents affect benthic organisms. Waves erode and remove substrate, causing changes in the biocenosis. Tides affect the zonation and movement of organisms. Currents change temperature and salinity, carrying minerals and affecting substrate consistency.
Physical Factors:
Illumination: Photosynthesis and animal vision depend on light penetration (limited to about 200m). Deep-sea organisms have adaptations to low light.
Temperature: Affects biogeographic zones, growth rates, sexual maturity, and longevity. It influences the vertical and horizontal zonation of benthic organisms and the form of animals. Some organisms’ metabolism depends on pressure (e.g., barophilic bacteria).
Chemical Factors:
Salinity: Affects osmotic pressure.
pH: Shows little variation (8.1-8.3).
Oxygen: Dissolved oxygen varies with water pollution and algal abundance.
Rocky Shore Communities:
The strong impact of waves and temporary emersion are important factors. Organisms have adaptations such as:
- Amphibious life adaptations (e.g., mussels).
- Adhesive or suction devices (e.g., gobies, spider crabs).
- Resistive bodies (e.g., snails, crabs).
- Life in cracks and holes (e.g., sea spiders).
Zonation of Species:
Coastal System or Phytalidae: Plants and algae.
Supralittoral Zone: Totally emersed; organisms adapted to this zone (e.g., Littorina peruviana).
Mollusks: Gastropods.
Crustaceans: Grapsus grapsus.
Algae: Ahnfeltia durvillaei.
Mesolitoral Zone (Intertidal): Continuous rises and falls.
Infralittoral Zone: Always submerged, rarely emersed (e.g., Megabalanus).
Circumlittoral Zone: Depth compatible with algae adapted to low light.