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OCEAN ACIDIFICATION & KELP GROWTH, Guiding Questions - Coggle Diagram
OCEAN ACIDIFICATION & KELP GROWTH
METHODOLOGY
Models (
https://www.frontiersin.org/articles/10.3389/fmars.2021.793977/full
)
Broch & Slagstad (2012)
emulate seasonal changes in growth and composition of the alga
wet and dry weights
simulates carbon and nitrogen reserves, with variable C/N ratio
based on published, environmental field data are presented and compared with corresponding data on growth and composition
Venolia et al (2020)
calibrated a Dynamic Energy Budget (DEB) model to data from the literature and field-based growth experiments in Rhode Island
temperature, irradiance, dissolved inorganic carbon concentration, and nitrate and nitrite concentration
modeled estimates for field S. latissima blade length were accurate despite underestimation of early season growth
no specific assumptions were made to include summer growth patterns such as tissue loss or reproduction
growth dynamics and blade length at the time of harvest
Sporophyte growth (hatchery cultivation)
Reproductive sori were stress-induced to release zoospores which were grown to gametophytes. Gametophytes developed for 3–5 months and were then sprayed onto the culture twine which was wrapped around plastic racks (collectors). These collectors were further cultivated for 4–6 weeks until the sporophytes attached were sufficiently mature to survive deployment at sea and when weather conditions were deemed suitable.
ECOSYSTEM ROLE
promote secondary productivity through provision of three-dimensional habitat structure, which supports a vast array of marine life, including species of commercial and conservation importance
Kelp forests represent some of the most productive and diverse habitats on Earth
on average, ~ 130 species and 8000 individuals on individual Laminaria hyperborea sporophytes in Norway
scientists note that effects of kelp appear to be reduced deeper in the water column, likely because of the way kelp calms water by dampening waves and currents
Kelps dominate rocky reefs in lower intertidal and shallow subtidal zones throughout temperate and subpolar regions of the world
provides a buffer for sensitive animals, allowing them to gradually adapt to acidic conditions
nutrient cycling, energy capture and transfer, and provide biogenic coastal defence
Changes in seaweeds are particularly important for coastal food webs, as they are key primary producers and often habitat-forming species
herbivores exposed to elevated pCO2-levels showed improved condition index, decreased consumption, but no significant change in feeding preference
The biogenic habitat structure provided by large canopy-forming seaweeds has been shown to offer protection to several commercial fish species
kelp canopies alter light, sedimentation, physical abrasion, flow dynamics, substratum availability and condition, and food quantity and quality (
https://www.sciencedirect.com/science/article/abs/pii/S0022098117300540
)
PH AND KELP
ocean acidification is the reduction in seawater pH due to absorption of CO2
long-term effects of climatic forcing may be buffered, or exacerbated, at different times of the annual cycle
fluctuations up to +/- 0.45 units
when they expected to see more acidic water, the water was actually less acidic relative to daytime measurements – a result they hypothesize was caused by the upwelling of acidic, low oxygen water during the day
kelp metabolically modifies seawater pH via photosynthesis and respiration in temperate coastal systems
growth and photosynthetic rates of juvenile kelp greater under fluctuating pH than static pH
found increased growth (measured as surface area increase), decreased tissue strength in a tensile strength test, and decreased chemical defense (phlorotannins) levels in seaweeds exposed to high pCO2-levels
prediction: surface oceanic pH decline by 0.4 units by 2100
increased wave energy in coastal ecosystems due to climate change, could have detrimental effects by reducing both habitat and food availability for herbivores
negative effect on photosynthesis
With the new high-resolution, vertical measurements of pH, dissolved oxygen, salinity and temperature, the researchers were able to distinguish patterns in the seawater chemistry around the kelp forest
pH fluctuations have a positive effect on kelp but this effect could be reversed in the future under OA
likely to impact the future ecological dynamics and productivity of habitats dominated by kelp
A suite of biochemical assays and in vivo chlorophyll a fluorescence parameters showed that elevated CO2 levels benefitted both of these algae, although their responses varied depending on light and nutrient availability
GROWTH
Unlike meat, fish and even vegetable farming practices, which use lots of resources, growing sugar kelp is low impact
Kelp spores are seeded onto spools of grow line and strung between buoys. This grid-shaped network of grow lines makes up the kelp farm
Kelp spores are seeded onto spools of grow line and strung between buoys. This grid-shaped network of grow lines makes up the kelp farm
it is hypothesised that when there are severe or sudden variations in seawater temperature, spore maturation/release is triggered or delayed (
https://www.frontiersin.org/articles/10.3389/fmars.2018.00218/full
)
Kelp is one of the fastest growing organisms on earth. Some species can grow as much as 2-3 feet per
day
potentially ameliorating species: speedy growth – up to 5 inches per day, during which it undergoes a large amount of photosynthesis that produces oxygen and removes carbon dioxide from the water
Organisms continuously adjust their physiological status as the physico-chemical environment around them fluctuates and changes (phenotypic plasticity)
in order to maintain optimal levels of energy production, fundamental to sustain cell repair, growth and reproductive investment
evolutionary aspects of ocean acidification, alone, and in combination with other stressors, have largely been overlooked
Sugar kelp grows quickly — from seedling to 15 feet in just a few months
UPWELLING
upwelling allow a surge in kelp and seaweed population by drawing up nutrient-rich, cold, acidic, low-oxygen water from the ocean depths
coolness is a key term, as the temperature will negatively effect the amount and spatial extent of kelp. If the water is too warmer than 20 degrees, the kelp will not thrive well
if the kelp-driven carbon fixation spurred by the nutrient inflow outpaces the amount of carbon brought up, kelp should start consuming anthropogenic carbon—alleviating acidification stress
In Monterey Bay, the effects of giant kelp are also influenced by seasonal upwelling, when deep, nutrient-rich, highly acidic water from the Pacific is pulled toward the surface of the bay
the mediation of processes that underpin the important ecosystem functions, such as biogeochemical cycling of macronutrients
CARBON SEQUESTER
giant kelp can relieve acidification by sequestering carbon diluted in the ocean as free carboxyl groups
7.4 kg of carbon sequestered per 100 m longline at the site during the cultivation period
This rate of sequestration is similar to that of several government-funded agroforestry schemes
increases the gas transfer velocity of atmospheric CO2 across the air–sea boundary layer into the ocean relative to adjacent sites without macroalgae present
macroalgal detritus is known to travel across community boundaries for kilometres over the space of several days
Kelp reaches its peak biomass. Once harvested, it can be processed into a variety of useful products, including organic fertilizer and biofuels
DEPENDENT VARIABLES
Growth
https://www.int-res.com/articles/meps/37/m037p035.pdf
Mann et al (1979)
Grendon (1985)
Mann & Mann (1979)
production was equal to growth times unit blade weight in the area of maximum blade biomass
overestimated actual production by 20 to 40% depending on whether overall sample production or individual blade production was considered
ra to compare the 2 techniques which they refer- red to as the exponential and the chordal models respectively. Be
relation between blade weight and length was made approximately equal to the relation observed at the time of initial measurement
Mann & Kirkman (1981)
Gerard & Mann (1979)
Mann (1972)
converted length increments to biomass increments by means of weight-length relations determined empirically
Types of Growth Measurements
SOMATIC
measured by weight gain, long thallus
PHYSIOLOGICAL
reproduction and koloidnya content
growth rate is calculated according to the weight gain of the seeds planted and expressed as a percent per day
ABSOLUTE GROWTH: determine the difference between the total and an increase of biomass of seaweed that have been planted. Weighing carried out under wet seaweed
weight gain seaweed = weight of the final seaweed - initial weight seaweed
DAILY GROWTH RATE: determine the rate of growth of seaweed that happens every day, the higher the daily growth rate shows the growth of seaweed, the better.
daily growth rate (g / day) = weight of the end of seaweed (g) - initial weight seaweed (g) / time maintenance (days)
SPECIFIC DAILY GROWTH RATE: widely used for the calculation of the scale of research because it uses exponential calculation so that it will get the value growth more specific
growth rate in percent per day = [weight of the plant after n days - weight initial plant)^(1/long maintenance in days) - 1] x 100%
PRODUCTION OF KELP: seaweed production yield calculation is done to determine the overall yields obtained and the level of production efficiency seaweed cultivated
seaweed biomass production (g / m) = [(weight of the end of seaweed (g) - initial weight seaweed (g)) x length of rope (m)]/the number of points of planting
OCEAN ACIDIFICATION
acidity increases with depth
additional energy absorbed by the world's oceans causes a 0.8°C rise in sea surface temperature over the past century.
rapid uptake of heat energy and CO2 by the ocean results in a series of concomitant changes in seawater carbonate chemistry, including reductions in pH and carbonate saturation state, as well as increases in dissolved CO2 and bicarbonate ions
Ocean acidification directly impacts shellfish, by dissolving shells and interfering with new shell growth
The ocean absorbs ~ 25% of the carbon dioxide humans emit into the atmosphere
26% increase in ocean acidity
One of the detrimental impacts of increased carbon in the atmosphere is its subsequent absorption by the planet’s oceans, which causes acidification
near the ocean’s surface, the water’s pH was slightly higher, or less acidic, suggesting the kelp canopy does reduce acidity
Those effects did not extend to the ocean floor, where sensitive cold-water corals, urchins and shellfish dwell and the most acidification has occurred
Ocean acidification also affects fish, whales, and sea birds who rely on shellfish and microscopic plankton for food and habitat.
affect many marine organisms in a variety of marine habitats from tropical to high-latitude ecosystems
co-occurring with other drivers of environmental change (including warming, eutrophication, hypoxia, eutrophication, pollution
calcifying (shell-forming) organisms, which show a tendency to exhibit strong sensitivities to ocean acidification
CO2 has the potential to influence the competitive abilities of these species following an increase in resource availability that, in turn, causes shifts in species dominance and community structure that affect long-term ecosystem persistence and stability
PRIMARY RESEARCH
Guiding Questions