STU1033 Aquatic Science & Daily Life Unit 2 2023/24 PDF

STU1033 Aquatic Science & Daily Life Sem 2 2023/24 LU2: Interaction between aquatic organisms and their habitats  At the end of the unit, you should be able to: 1. Classify categories of aquatic life. 2. Describe factors influencing the assemblage aquati...

STU1033 Aquatic Science & Daily Life Sem 2 2023/24 LU2: Interaction between aquatic organisms and their habitats  At the end of the unit, you should be able to: 1. Classify categories of aquatic life. 2. Describe factors influencing the assemblage aquatic organisms in their habitat. 3. Aware and take precaution of the selected dangerous and venomous aquatic animals. 4. Understand the food chains and webs. Acknowledgement: Notes are adapted from OpenCourseWare@UNIMAS Three categories of aquatic life: Small size – microscope aid needed to see drift along with the river/sea flow Phytoplankton (plant) -live in the well-lit surface layer, may appear as a green discoloration of the water due to the presence of chlorophyll within PLANKTON their cells Zooplankton (animal)- some are small, some are big e.g. jellyfish. Feeds on phytoplankton. Pelagic organisms that can actively swim against the current. Vertebrates (with backbone) and invertebrates NEKTON (without backbone). community of organisms which live on, in, or near the sea beds (benthic zone) adapted to deep-water pressure, cannot survive BENTHOS in the upper parts of the water column Energy source -organic matter from higher up in the water column which drifts down to the depth. Assemblage aquatic organisms in their habitats: Temperature Oxygen levels Light profiles Food sources  Primary productivity Phytoplankton blooms makes up much of the ocean's primary = the rate at which energy is converted to productivity in Earth's oceans. organic substances. Photosynthetic producers (photoautotrophs), obtain energy and nutrients by harnessing sunlight Chemosynthetic producers (chemoautotrophs), obtain chemical energy through oxidation. Nearly all of Earth’s primary productivity is generated by photoautotrophs. In marine environments, the two principal categories of producers are pelagic phytoplankton, which float freely in the ocean, and benthic algae, which live at or near the ocean’s floor.  Primary Productivity depends on: photosynthesis & light respiration of algae & aquatic plants [nutrients] for example nitrate & phosphate High level of organic matter, abundant plant growth, poor eutrophic – high rate clarity, stratified with O₂ poor bottoms. Low levels of organic matter, tend to be deep and clear, O₂ rich bottom oligotrophic – low rate supports cold water fish such as trout. Nutrients are limiting. mesotrophic – intermediate rate More organic matter, O₂ level in bottom is low. A dead zone is an area where O₂ dystrophic – very low rate levels fall below 2ppm.  Interaction of heat & light with organisms: 1. Algal density affects the heating of lakes? more algae, light reflected out = less heat less algae, better water transparency = deeper thermocline & warmer epilimnion 2. Fish predation can cool lakes? algal density controlled by zooplankton grazing 3. Global warming produces clearer lakes? more forest fire, low stream flow, less nutrient transport low, less algae warmer lake = thermal stratification prevent mixing, less nutrient recycling Food chains and food webs:  Exercise: Create your own food webs with at least 3 food chains involved. Behaviour of selected aquatic species: Feeding Frenzy Food attracted some fish Other fish attracted as well (thinking about easy food). More fish attracted to the scene, the more distressed the scene. becomes, as the splashing increases. They enter the frenzied state. Behaviour of selected aquatic species: Schooling a group of fish move together in coordinated fashion and form patterns. range from simple ellipsoids to complicated vortex arrangements depending on the fish species and circumstances. often have a regular spacing between individual and move very uniformly in the same direction. function primarily as an anti-predation mechanism fish move together, but are not simply all headed for the same goal (i.e. towards a food source). Behaviour of selected aquatic species: Migration "anadromous" fish: mature in salt water but spawn in fresh water e.g. salmon and ‘terubok’. "catadromous” fish: grow in fresh water and spawn in the sea e.g. eel and Epinephelus bleekeri. Behaviour of selected aquatic species: Sex reversal Also known as “protandrous” fish. Normal anatomical process e.g. clownfish, seabass. Exposed to endocrine disrupters (e.g. tilapia): masculinization by exposure to androgens feminization by exposure to estrogens Behaviour of selected aquatic species: Solitary aquatic animal Spends a majority of their lives without others of their species, with possible exceptions for mating and raising their young. Several individuals can share the same body of water. E.g. Platypus. Behaviour of selected aquatic species: Highly socialized group Associated with specific actions. For example: A communication to begin travel: breeching (jumping out of the water and landing on one’s side). A communication indicating the travel is over : upside-down lob-tailing (rolling over to expose the ventral side at the water surface, lifting the flukes above the water, and then slapping them down onto the water surface). Dolphins communicate with their pods and large groups usually through whistles. Dolphins in distress seem to use a special whistle that indicates help is needed. The pod or group usually responds quickly. E.g. Dolphin.  Behaviour of selected aquatic species: Anti-predation behaviour Protects itself by inflating its belly to make itself look bigger, e.g. puffer fish/ blowfish Almost all species of puffer fish contain toxin (called tetrodotoxin) that can be 1200 times stronger than cyanide. The sand-dwelling octopus mimicking the swimming behavior and coloration of sand-dwelling flounder. Each species was exceptionally well camouflaged when stationary. [see http://www.break.com/video/test-1945423] When threatened by predator respond by secreting a stream of dark ink (pigment) e.g. squid, cuttlefish, and octopuses. Behaviour of selected aquatic species: Territorial behaviour To show off ‘power’, to control home territory To protect eggs and the young E.g. crocodiles, fighting fish (Betta spp.)  Behaviour of selected aquatic species: Others Example of Behaviour aquatic animal Nesting-site fidelity turtles Natal homing Cannibalism Bigger size animal eats the smaller size animals. Natural phenomenon in order Catfish to control population size. Lack of food, to minimize competition (for survival).  Dangerous and Venomous Aquatic Organisms: Terms Definition substances that can cause disturbances to organisms, usually by chemical Poison reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism. Toxin poisons produced via some biological function in nature (bio-toxin). biological toxins that are injected by a bite or sting to cause their effect Venom (venom glands or highly specialized secretory cells, delivered by a venom apparatus into other animals)  Dangerous and Venomous Aquatic Organisms: Dangerous organism: Venomous organisms: 1. Box jellyfish Piranha River/ Freshwater 2. Stonefish South American 3. Sea snakes Crocodiles 4. Cone snails Estaurine 5. Blue-ringed octopus Marsh/Saltwater 6. Stingray River Do you know any real-life Sharks Open sea stories of people attacked Marine life by any of these organisms? What happened? - The End of Unit 2 -