The document encompasses a detailed summary of the course Seaweed Biology and Cultivation Summary. The 13 page document is filled with every important aspect of the course, including important images.
Potential production is the theoretical max. production of a crop. It is limited by nutrients and environmental
factors. The relative growth rate (RGR) under assumed unlimited growth is 0.15/ day for seaweeds. RGR =
NAR (growth/leaf area) * SLA (Leaf area/leaf mass) * LMR (Leaf mass/ plant mass). The tidal range is the
difference in vertical height between lowest tide and the highest tide. These areas are unstable is temperature due
to desiccation but more viable due to light exposure. Tides occur due to the gravitational pull of the moon.
Spring tides occur when the moon an the sun are aligned, causing higher tides. Seaweed leaves have great
flexibility to reduce drag in an environment with high wave activity.
Temperature increases leads to higher enzyme activity and higher fluidity of membranes. Too high of a
temperature could lead to over-fluidity, photorespiration and denaturation of enzymes. Temperature fluctuates
higher in tidal waters because the water is more shallow. In general the temperature effects are smaller in water
because of the thermal capacities of water.
Salinity is an important factor in both fresh – and seawater. It is increased by evaporation and tides (mixing of
water) and decreased by the sinking of salt and river influxes. Water potential always flow from high to low
potential. Dissolved minerals like salts decrease the water potential – waters with high salt content will thus
have a low water potential.
Nutrient uptake is actively carried out by import enzymes. Enzyme characteristics: a high Vmax is correlated
with a high Ks. A high Vmax is also correlated with a lower affinity. Ks in inversely related to affinity. High
nutrient availability habitats produce High Vmax enzymes with low affinities. The nutrient balance: increased
by fish farming/ deposition/ bacterial fixation and terrestrial inflow of polluted water (agriculture). Decreased by
plant uptake and nutrient sinking.
1.2 Cultivation
Seaweeds have alternation of life cycles making them difficult for cultivation. Gametophytic and sporophytic
life cycles alternate with each other. Temperature optima for the different life stages may differ. A weed is a
plant that negatively affects a crops performance with economical consequences. They are competition for
resources and habitats to pests. Seaweed herbivore control: use of herbivores (weed specific), desiccation,
environmental control and the use of resistant varieties. Breeding in seaweeds is hard however, there is little
genomic work in seaweeds. Extensive cultivation involves the traditional method of cultivation, in the natural
habitat of the seaweed. Offshore cultivation brings some practical issues – transportation, and the roughness of
the sea. Offshore cultivation could be coupled with windmill parks (No ships/ infrastructure is already present).
Intensive cultivation involved cultivation outside of natural habitats – such as on shore tanks. Advantages of the
latter is fine tuning of conditions (light, nutrient, pest control) to maximize growth. Disadvantages of intensive
cultivation is the supply of seawater (including CO2 addition), temperature regulation (day/night), movement of
water to avoid boundary layers and the costs of nutrient addition only applied: close to the coasts, use of
vegetative propagation and only applied to high-end products.
Ecological effects of seaweed cultivation: contribution to local biodiversity, biofiltering of toxic compounds
Phosphate crisis could be solved by cultivating seaweed in terrestrial inflow areas where phosphate levels are
high. Challenges for integrated multi-trophic aquaculture dilution of nutrients/ composition of wastes does
not match the seaweed demand. Negative ecological effects include: introduction of invasive species. They can
destroy natural coastal areas and shade lower (benthic) communities. Invasive species are good competitors for
resources, are plastic (adapt to new conditions) and are resistant to a wide range of pests. Invasive species
function well because of competition/ enemy release.
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, Seaweeds : Biology and diversity 2.1
Algae : anything that has plastids and is not a land plant. Diverges from single celled algae to giant seaweeds
(diverse evolutionary lineages). Algae preform oxygenic photosynthesis, the common type of photosynthesis that
produces oxygen. A wide accessory of pigments is required for a wide range of light absorption (compared to
chlorophyll-a) because the light is absorbed by the water. Optimizing photosynthesis efficiency: Phototaxis
involves sensing light and responding by positioning optimally towards the light source. Preformed by light-
sensing proteins (Phototrophin, phytochrome). Positioning is an active process (osmotic activity, gas vacuoles,
flagellum movement).
Microalgae occur unicellular, in colonies and filaments (branched). Macroalgae can be observed with the naked
eye, can be a singe multinucleate cell. Parenchymatous algae require plasmodesmata for cell-to-cell transport of
assimilates. Algal reproduction is asexual – via zoospores (flagellate) and autospores/aplanospores (non-
flagellate). Akinetes: cells that survive unfavourable conditions, contain large cell walls and accumulation of
storage materials. Isogamous: male and female gamete are both mobile and have the same size. Anisogamous:
male and female gametes are both mobile and one gamete is larger/ behaves differently. Oogamous: male
gametes fuse with larger, immobile female egg cell.
In 5 out of the 7 eukaryotic kingdoms,
photosynthetic organisms occur. These organisms
occur in great diversity. Ancient cyanobacteria
generated the first oxygen in the earth’s
atmosphere. The fixed CO2 formed carbonate rock
formations and fossil fuels deposits. 2.2-2.4 billion
year ago – the great oxidation event, afterwards
sufficient oxygen was present in the atmosphere for
eukaryotic life forms. Although photosynthesis and
respiration are balanced, oxygen did accumulate in
the atmosphere. This was possible because 1.
carbohydrates where buried as sediments and not
degraded by microorganisms fossil fuels, 2.
Generation of sedimentary carbonate minerals
(calcium carbonate). Ozone production by algae allowed terrestrial life.
Mechanisms to prevent C02 diffusion outside of cell (C02 migrates freely across membranes): C02 is converted
to CHO-, the polar molecule cannot migrate (by enzyme carbonic anhydrase).
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