Marine Ecosystems: Photosynthesis, Chemosynthesis, Nutrients & Food Webs

Original energy source for photosynthesis and chemosynthesis

Photosynthesis → Sunlight; Chemosynthesis → Hydrogen sulfide (H₂S)

Photosynthesis

Converts inorganic minerals into organic compounds using light; Reactants: CO₂ + H₂O; Products: C₆H₁₂O₆ + O₂; Uses chlorophyll and minerals like Mg, NO₃⁻, PO₄³⁻

Elements found in all carbohydrates, lipids, and proteins

Carbon, Hydrogen, Oxygen

Polymers and their monomers

Cellulose → Glucose; Lipids → Fatty acids + Glycerol; Protein → Amino acids; Starch → Glucose

Nutrients present in agricultural fertilizers

PO₄³⁻, NO₃⁻, Mg, K (any two)

Limiting factors of photosynthesis

Light intensity, temperature, CO₂, and nutrient availability (each can increase or decrease productivity)

Runoff

Water flowing from land to rivers/oceans; carries dissolved minerals; occurs after rainfall or snowmelt

Benefits of runoff to marine organisms

Provides nutrients (e.g., Ca for shells); producers use them for photosynthesis (Mg, NO₃, PO₄); increases productivity

Harmful effects of runoff to marine organisms

Causes algal blooms/eutrophication; releases toxins; lowers O₂ during decomposition; blocks light; creates dead zones

Role of bacteria in a food web

Decomposers recycle nutrients; convert organic → inorganic materials; nutrients reused by producers

Predator-prey relationships

Cyclical pattern; prey increase → predator increase; predator decrease → prey increase; includes lag time

Calculating % energy transferred

% = (Energy at higher level ÷ Energy at lower level) × 100; Example: (1,700 ÷ 36,000) × 100 = 4.72%

Sunlight assimilation by producers

Only 1-3% of sunlight is assimilated; some sunlight reflected; not all absorbed by chlorophyll; not all wavelengths absorbed

Energy transfer to consumers

Consumers only receive ~10% of energy from the previous trophic level due to heat loss from respiration, not all parts eaten, loss in excretion/egestion, and undigested material in feces

Biological uses for nutrients

Nitrogen → Amino acids/proteins/DNA/RNA; Carbon → Proteins/carbs/lipids/nucleic acids; Phosphorus → DNA/RNA/bone/ATP/membranes; Magnesium → Chlorophyll/enzymes

Symbiotic relationship between Riftia and chemosynthetic bacteria

Bacteria use H₂S for chemosynthesis to feed tubeworms (mutualism)

Symbiotic relationship between coral polyps and zooxanthellae

Algae provide food; coral provides shelter (mutualism)

Symbiotic relationship between sea lice and salmon

Parasitic — lice feed on salmon tissue

Symbiotic relationship between manta rays and remora fish

Commensal — remora gets food/transport; manta unaffected

Similarities between coral/zooxanthellae and vent bacteria/tubeworm mutualism

Both have endosymbiont producers; endosymbiont gains habitat; producers provide nutrients/energy; both use CO₂ + H₂O → C₆H₁₂O₆

Calcium in rocks entering the ocean

Weathering and erosion dissolve calcium into runoff entering the ocean

Calcium reaching the seabed

Taken up by producers and consumers; after death/feces → sinks to seabed

Overharvesting and the calcium cycle

Removes calcium permanently; less Ca available in the cycle

Calcium returning to the surface from the seabed

Upwelling (wind-driven or caused by seamounts/ridges)

Relationship between CO₂ in air and CO₂ in water

As atmospheric CO₂ increases, ocean CO₂ increases; due to equilibrium gas exchange and atmospheric dissolution

Chemistry of ocean acidification

CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻; increased H⁺ lowers pH (acidic); less CaCO₃ formed → weaker shells

Calcium nutrient cycle

Weathering/erosion → runoff → surface → uptake into food web → death/feces → seabed → upwelling to surface; harvesting removes Ca permanently

Vocab matching topics

Trophic levels; pyramid of energy (boxes, not triangles); % energy transfer; roles of producers, consumers, decomposers