Welcome to the I Can't Sleep podcast where I help you drift off one fact at a time.
I'm your host Benjamin Boster.
Thanks for listening,
And don't forget to follow the show if it helps you rest.
Today's episode is about kelp forests.
Kelp forests are underwater areas with a high density of kelp,
Which covers a large part of the world's coastlines.
Smaller areas of anchored kelp are called kelp beds.
They are recognized as one of the most productive and dynamic ecosystems on earth.
Although algal kelp forests combined with coral reefs only cover 0.
1% of earth's total surface,
They account for 0.
9% of global primary productivity.
Kelp forests occur worldwide,
Throughout temperate and polar coastal oceans.
In 2007,
Kelp forests were also discovered in tropical waters near Ecuador.
Physically formed by brown macroalgae,
Kelp forests provide a unique habitat for marine organisms and are a source for understanding many ecological processes.
Over the last century,
They have been the focus of extensive research,
Particularly in tropic ecology,
And continue to provoke important ideas that are relevant beyond this unique ecosystem.
For example,
Kelp forests can influence coastal oceanographic patterns and provide many ecosystem services.
The term kelp refers to marine algae belonging to the order laminary eels.
Though not considered a taxonomically diverse order,
Kelps are highly diverse structurally and functionally.
The most widely recognized species are the giant kelps,
Although numerous other genera are described.
A wide range of sea life use kelp forests for protection or food,
Including fish.
In the North Pacific,
Kelp forests,
Particularly rockfish and many invertebrates,
Such as amphipods,
Shrimp,
Marine snails,
Bristle worms,
And brittle stars.
Many marine mammals and birds are also found,
Including seals,
Sea lions,
Whales,
Sea otters,
Gulls,
Terns,
Snowy egrets,
Great blue herons,
And cormorants,
As well as some shorebirds.
Frequently considered an ecosystem engineer,
Kelp provides a physical substrate and habitat for kelp forest communities.
In algae kingdom protista,
The body of an individual organism is known as a thallus,
Rather than as a plant,
Kingdom plantae.
The morphological structure of a kelp thallus is defined by three basic structural units.
The holdfast is a root-like mass that anchors the thallus to the seafloor,
Though unlike true roots,
It is not responsible for absorbing and delivering nutrients to the rest of the thallus.
The stipe is analogous to a plant stalk,
Extending vertically from the holdfast and providing a support framework for other morphological features.
The fronds are leave for blade-like attachments extending from the stipe,
Sometimes along its full length,
And are the sites of nutrient uptake and photosynthetic activity.
In addition,
Many kelp species have pneumatocytes,
Or gas-filled bladders,
Usually located at the base of fronds near the stipe.
These structures provide the necessary buoyancy for kelp to maintain an upright position in the water column.
The environmental factors necessary for kelp to survive include hard substrate,
Usually rock or sand,
High nutrients,
E.
G.
Nitrogen,
Phosphorus,
And light,
Minimal annual irradiance dose greater than 50 e per square meter.
Especially productive kelp forests tend to be associated with areas of significant oceanographic upwelling,
A process that delivers cool,
Nutrient-rich water from depths to the ocean's mixed surface layer.
Water flow and turbulence facilitate nutrient assimilation across kelp fronds throughout the water column.
Water clarity affects the surface of kelp forests,
And affects the depths to which sufficient light can be transmitted.
In ideal conditions,
Giant kelp can grow as much as 30-60 cm vertically per day.
Some species,
Such as Nereocystis,
Are annuals,
While others,
Such as Eisenia,
Are perennials,
Living for more than 20 years.
In perennial kelp forests,
Maximum growth rates occur during upwelling months,
Typically spring and summer,
And diebacks correspond to reduced nutrient availability,
Shorter photoperiods,
And increased storm frequency.
Kelps are primarily associated with temperate and arctic waters worldwide.
Of the more dominant genera,
Laminaria is mainly associated with both sides of the Atlantic Ocean and the coasts of China and Japan.
Heclonia is found in Australia,
New Zealand,
And South Africa.
Macrocystis occurs throughout the Northeastern and Southeastern Pacific Ocean,
Southern Ocean,
Archipelagos,
And in patches around Australia,
New Zealand,
And South Africa.
The region with the greatest diversity of kelps,
Greater than 20 species,
Is the Northeastern Pacific,
From north of San Francisco,
California to the Aleutian Islands,
Alaska.
Although kelp forests are unknown in tropical surface waters,
A few species of Laminaria have been known to occur exclusively in tropical deep waters.
This general absence of kelp from the tropics is believed to be mostly due to insufficient nutrient levels associated with warm oligotrophic waters.
One recent study spatially overlaid the requisite physical parameters for kelp with mean oceanographic conditions and produced a model predicting the existence of subsurface kelps throughout the tropics worldwide to depths of 200 meters.
For a hot spot in the Galapagos Islands,
The local model was improved with fine-scale data and tested.
The research team found thriving kelp forests in all eight of their sampled sites,
All of which have been predicted by the model,
Thus validating their approach.
This suggests that their global model might actually be fairly accurate,
And if so,
Kelp forests would be prolific in tropical subsurface waters worldwide.
The importance of this contribution has been rapidly acknowledged within the scientific community and has prompted an entirely new trajectory of kelp forest research,
Highlighting the potential for kelp forests to provide marine organisms spatial refuge under climate change and providing possible explanations for evolutionary patterns of kelps worldwide.
The architecture of a kelp forest ecosystem is based on its physical structure,
Which influences the associated species that define its community structure.
Structurally,
The ecosystem includes three guilds of kelp and two guilds occupied by other algae.
Canopy kelps include the largest species and often constitute floating canopies that extend the ocean surface.
Stipitate kelps generally extend a few meters above the seafloor and can grow in dense aggregations.
Prostrate kelps lie near and along the seafloor.
The benthic assemblage is composed of other algal species,
E.
G.
Filamentous and folios functional groups,
Articulated corallines,
And sessile organisms along the ocean bottom.
Encrusting coralline algae directly and often extensively cover geologic substrate.
Multiple kelp species often coexist within a forest.
The term understory canopy refers to the stipitate and prostrate kelps.
For example,
A macrocystis canopy may extend many meters above the seafloor towards the ocean surface,
While an understory of the kelps isenia and pterygophora reaches upward only a few meters.
Beneath these kelps,
A benthic assemblage of folios red algae may occur.
The dense vertical infrastructure with overlying canopy forms a system of microenvironments similar to those observed in a terrestrial forest,
With a sunny canopy region,
A partially shaded middle,
And darkened seafloor.
Each guild has associated organisms,
Which vary in their levels of dependence on the habitat,
And the assemblage of these organisms can vary with kelp morphologies.
For example,
In California,
Macrocystis periphera forus,
The nudibranch Mellabea leonina,
And skeleton shrimp,
Caprela californica,
Are closely associated with surface canopies.
The kelp perch Brachystis frenatus,
Rockfish Sebastis spp.
,
And many other fishes are found within the stipitate understory.
Brittle stars and urban snails Tagula spp.
Are closely associated with the kelp holdfast,
While various herbivores,
Such as sea urchins and abalone,
Live under the prostrate canopy.
Many sea stars,
Hydroids,
And benthic fishes live among the benthic assemblages.
Solitary corals,
Various gastropods,
And echinoderms live over the encrusting coralline algae.
In addition,
Pelagic fishes and marine mammals are loosely associated with kelp forests,
Usually interacting near the edges as they visit to feed on resident organisms.
Classic studies in kelp forest ecology have largely focused on trophic interactions,
The relationships between organisms and their food webs,
Particularly the understanding and top-down trophic processes.
Bottom-up processes are generally driven by the abiotic conditions required for primary producers to grow,
Such as availability of light and nutrients,
And the subsequent transfer of energy to consumers at higher trophic levels.
For example,
The occurrence of kelp is frequently correlated with oceanographic upwelling zones,
Which provide unusually high concentrations of nutrients to the local environment.
This allows kelp to grow and subsequently support herbivores,
Which in turn support consumers at higher trophic levels.
By contrast,
In top-down processes,
Predators limit the biomass of species at lower trophic levels through consumption.
In the absence of predation,
These lower-level species flourish because resources that support their energetic requirements are not limiting.
In a well-studied example from Alaskan kelp forests,
Sea otters control populations of herbivorous sea urchins through predation.
When sea otters are removed from the ecosystem,
For example by human exploitation,
Urchin populations are released from predatory control and grow dramatically.
This leads to increased herbivore pressure on local kelp stands.
Deterioration of the kelp itself results in the loss of physical ecosystem structure and subsequently the loss of other species associated with this habitat.
In Alaskan kelp forest ecosystems,
Sea otters are the keystone species that mediates this trophic cascade.
In Southern California,
Kelp forests persist without sea otters and the control of herbivorous urchins is instead mediated by a suite of predators,
Including lobsters and large fishes,
Such as the California sheephead.
The effect of removing one predatory species in this system differs from Alaska because redundancy exists in the trophic levels and other predatory species can continue to regulate urchins.
However,
The removal of multiple predators can effectively release urchins from predatory pressure and allow the system to follow trajectories towards kelp forest degradation.
Similar examples exist in Nova Scotia,
South Africa,
Australia,
And Chile.
The relative importance of top-down versus bottom-up control in kelp forest ecosystems and the strengths of trophic interactions continue to be the subject of considerable scientific investigation.
The transition from macroalgal,
I.
E.
Kelp forest,
To denuded landscapes dominated by sea urchins or urchin barrens is a widespread phenomenon,
Often resulting from trophic cascades like those described earlier.
The two phases are regarded as alternative stable states of the ecosystem.
The recovery of kelp forest from barren states has been documented following dramatic perturbations,
Such as urchin disease or large shifts in thermal conditions.
Recovery from intermediate states of deterioration is less predictable and depends on a combination of abiotic factors and biotic interactions in each case.
Though urchins are usually the dominant herbivores,
Others with significant interaction strengths include sea stars,
Isopods,
Kelp crabs,
And herbivorous fishes.
In many cases,
These organisms feed on kelp that has been dislodged from substrate and drifts near the ocean floor,
Rather than expend energy searching for intact thalli in which to feed.
When sufficient drift kelp is available,
Herbivorous grazers do not exert pressure on attached thalli.
When drift subsidies are unavailable,
Grazers directly impact the physical structure of the ecosystem.
Many studies in Southern California have demonstrated that the availability of drift kelp specifically influences the foraging behavior of sea urchins.
Drift kelp and kelp-derived particulate matter have also been important in subsidizing adjacent habitats,
Such as sandy beaches and the rocky intertidal.
Another major area of kelp forest research has been directed at understanding the spatial temporal patterns of kelp patches.
Not only do such dynamics affect the physical landscape,
But they also affect species that associate with kelp for refuge or foraging activities.
Large-scale environmental disturbances have been offered important insights concerning mechanisms and ecosystem resilience.
In addition to ecological monitoring of kelp forests before,
During,
And after such disturbances,
Scientists try to tease apart the intricacies of kelp forest dynamics,
Using experimental manipulations.
By working on smaller spatial-temporal scales,
They can control for the presence or absence of specific biotic and abiotic factors to discover the operative mechanisms.
For example,
In Southern Australia,
Demonstrated that the relative amount of Echlinea radiata in a canopy could be used to predict understory species assemblages.
Consequently,
The proportion of E radiata can be used as an indicator of other species occurring in the environment.
Kelp forests have been important to human existence for thousands of years.
Indeed,
Many now theories that the first colonization of the Americas was due to fishing communities following the Pacific kelp forest during the last ice age.
One theory contends that the kelp forests that would have stretched from the Northeast Asia to the American Pacific coast would have provided many benefits to ancient boaters.
The kelp forests would have provided many sustenance opportunities,
As well as acting as a type of buffer from rough water.
Besides these benefits,
Researchers believe that the kelp forests might have helped early boaters navigate,
Acting as a type of kelp highway.
Theorists also suggest that the kelp forests would have helped these ancient colonists by providing a stable way of life and preventing them from having to adapt to new ecosystems and develop new survival methods,
Even as they traveled thousands of miles.
Modern economies are based on fisheries of kelp-associated species,
Such as lobster and rockfish.
Humans can also harvest kelp directly to feed aquaculture species such as abalone and to extract the compound alginic acid,
Which is used in products like toothpaste and antacids.
Kelp forests are valued for recreational activities,
Such as scuba diving and kayaking.
The industries that support these sports represent one benefit related to the ecosystem,
And the enjoyment derived from these activities represents another.
All of these are examples of ecosystem services provided specifically by kelp forests.
The Monterey Bay Aquarium was the first aquarium to exhibit an alive kelp forest.
Kelp forests grow in rocky places along the shore that are constantly eroding,
Carrying material out to the deep sea.
The kelp then sinks to the ocean floor and stores the carbon,
Where it is unlikely to be disturbed by human activity.
Researchers from the University of Western Australia estimated kelp forests around Australia sequestered 1.
3 to 2.
8 teragrams of carbon per year,
Which is 27 to 34 percent of the total annual blue carbon sequestered in the Australian continent by tidal marshes,
Mangrove forests,
And seagrass beds.
Every 200 million tons of carbon dioxide are being sequestered by macroalgae,
Such as kelp.
In the 2010s,
Northern California lost 95 percent of its kelp ecosystems due to marine heatwaves.
Kelp bed recovery efforts in California are primarily focused on sea urchin removal,
Both by scuba divers and by sea otters,
Which are natural predators.
A brown alga,
An invasive species first spotted in 2003,
Has also been a concern.
The sunflower sea star is an important keystone species,
Which helps control sea urchin abundance.
But an outbreak of sea star wasting disease and a vulnerability to climate change has led to its critical endangerment.
Researchers at the Bodega Marine Laboratory of UC Davis are developing replanting strategies,
And volunteers of the Orange County Coast Keeper Group are replanting giant kelp.
Humboldt State University began cultivating bull kelp in its research farm in 2021.
Research efforts at the state level to prevent kelp forests collapse in California were announced in July 2020.
At the federal level,
H.
R.
4458,
The Keeping Ecosystems Living and Productive Kelp Act,
Introduced July 29,
2021,
Seeks to establish a new grant program within NOAA for kelp forest restoration.
Ocean Rainforest,
A Faroe Islands-based company,
Secured $4.
5 million in U.
S.
Government funding to grow giant kelp on an 86-acre farm off the coast of Santa Barbara,
California.
The United Nations Environment Program Norwegian Blue Forest Network 2023 report titled Into the Blue – Securing a Sustainable Future for Kelp Forests documents a global decline in kelp forests,
With an annual reduction rate of 1.
8 percent.
Over the past 50 years,
40 to 60 percent of these ecosystems have degraded due to factors such as climate change,
Poor water quality,
And overfishing.
The report underscores the urgency of implementing global conservation efforts and emphasizes the need for international cooperation to adopt area-based management strategies.
These strategies aim to mitigate the aforementioned impacts and enhance the resilience and sustainability of kelp forests.
Kelp forest restoration,
Practiced in 16 countries over 300 years,
Has gained momentum,
Particularly from 2009 to 2019,
Involving diverse societal sectors such as academia,
Governments,
And businesses.
Large-scale restoration successes demonstrate its feasibility,
With the best outcomes often near existing kelp forests,
Emphasizing the importance of preventing their decline.
However,
Challenges persist,
Including the need for cost-effective methods,
Funding mechanisms,
And adaptations to climate change.
This restoration work not only supports ecological recovery,
But also offers significant social and economic benefits,
Aligned with the United Nations Sustainable Development Goals,
SDGs,
And underscores the importance of multi-sector collaboration.
Aquaculture of giant kelp,
Macrocystis pyrifera,
Is the cultivation of kelp for uses such as food,
Dietary supplements,
Or potash.
Giant kelp contains iodine,
Potassium,
Other minerals,
Vitamins,
And carbohydrates.
At the beginning of the 20th century,
California kelp beds were harvested for their potash.
Commercial interest increased during the 1970s and the 1980s due to the production of alginates,
And also for biomass production for animal feed due to the energy crisis.
However,
Commercial production for M.
Pyrifera never developed.
With the end of the energy crisis and the decline in alginate prices,
Research into farming Macrocystis declined.
The supply of M.
Pyrifera for alginate production relied heavily on restoration and management of natural beds during the early 1990s.
Other functions,
Such as substrate stabilization,
Were explored in California,
Where the kelp bed project transplanted adult specimens to increase the stability of the harbor and promote diversity.
Research is investigating its use as feed for other aquaculture species,
Such as fish.
China and Chile are the largest producers of aquatic plants and algae,
Each producing over 300,
000 tons in 2007.
How much of this total can be attributed to M.
Pyrifera is unclear.
Both countries culture a variety of species.
In Chile,
50% of the production involves pheophytes,
And the other 50% is rhodophytes.
China produces a larger variety of seaweeds,
Including chlorophytes.
Experiments in Chile are exploring hybrids of M.
Pyrifera and M.
Integrifolia.
Kelp farming development has been ongoing in Oregon and British Columbia.
Startups have begun leasing water in Alaska to create M.
Pyrifera at a large scale.
In the 2010s,
Northern California lost 95% of its kelp ecosystems due to marine heat waves.
Kelp bed recovery efforts in California are primarily focusing on sea urchin removal,
Both by scuba divers and by sea otters,
Which are natural predators.
A brown algae,
An invasive species first spotted in 2003,
Has also been a concern.
Researchers at the Bodega Marine Laboratory of UC Davis are developing replanting strategies,
And volunteers of the Orange County Coast Keeper Group are replanting giant kelp.
Humboldt State University began cultivating bull kelp in its recent years.
Humboldt State University began cultivating bull kelp in its recent years.
Research efforts at the state level to prevent kelp forest collapse in California were announced in July 2020.
At the federal level,
H.
R.
4458,
The Keeping Ecosystems Living and Productive Kelp Act,
Introduced July 29,
2021,
Seeks to establish a new grant program within NOAA for kelp forest restoration.
Ocean Rainforest,
A Faroe Islands-based company,
Secured $4.
5 million in U.
S.
Government funding to grow giant kelp on an 86-acre farm off the coast of Santa Barbara,
California.
