Kelp Forest Monitoring & Remote Sensing

In the 16th episode of Ecobot’s Convergence of Wetland Science and Technology webinar series, we heard from experts involved in the KelpRes project in Galway, Ireland about the ecological importance of kelp forests.

Topics

• Natural and Nature-Based Features (NNBF) for Coastal Resilience
• Kelp Forest Monitoring and Remote Sensing

Moderator

Jeremy Schewe, PWS, Chief Scientific Officer, Ecobot?

Presenters & Panelists

Kathryn Schoenrock-Rossiter, PhD, Postdoctoral Researcher, National University of Ireland Galway

Aaron Golden, PhD, College Lecturer, National University of Ireland Galway

Stacy Krueger-Hadfield, PhD, Assistant Professor, University of Alabama at Birmingham

Natural and Nature-Based Features (NNBF) for Coastal Resilience

Related USACE Initiatives?

United States Army Corps of Engineers (USACE)’s Engineering With Nature (EWN)?

USACE’s Engineering with Nature (EWN) initiative enables the development of infrastructure that is resilient and maximizes the delivery of economic, social, and environmental benefits. The initiative aims to:

• Use science and engineering to produce operational efficiencies supporting sustainable delivery of project benefits.
• Use natural processes to maximum benefit, thereby reducing demands on limited resources, minimizing the environmental footprint of projects, and enhancing the quality of project benefits.
• Broaden and extend the base of benefits provided by projects to include substantiated economic, social, and environmental benefits.
• Use science-based collaboration to organize and focus interests, stakeholders, and partners to reduce social friction, resistance, and project delays while producing more broadly acceptable projects.

International Guidelines on Natural and Nature-Based Features (NNBF) for Flood Risk Management

In 2021, EWN released international guidelines on NNBF for Flood Risk Management, which “provide practitioners with the best available information concerning the conceptualization, planning, design, engineering, construction, and maintenance of NNBF to support resilience and flood risk reduction for coastlines, bays, and estuaries, as well as river and freshwater systems.” The guidelines examine areas that have been or will be submerged, and projections for coastline changes due to climate change. This information is critical for scientists, policymakers, developers, and engineers in considering intelligent planning.

On September 14, 2021, USACE released a 20-chapter publication on NNBF guidelines (linked here), which is broken into 3 major sections:

1. Overarching themes
2. Coastal features
3. Fluvial Features

Tying it back to kelp, “kelp forests are the ecotone between the deeper open sea and our coastlines and estuaries,” says Jeremy Schewe, PWS, Chief Scientist at Ecobot. “Kelp is a keystone species. It’s a critical species in providing habitat, nutrients, and hunting grounds for many species that are on international critical and watch lists, as well as threatened or endangered, while also supporting species that are very common.”

Kelp Forest Overview

Kathryn Schoenrock-Rossiter, PhD, Postdoctoral Researcher, National University of Ireland Galway; Aaron Golden, PhD, College Lecturer, National University of Ireland Galway; and

Stacy Krueger-Hadfield, PhD, Assistant Professor, University of Alabama at Birmingham are each involved with the KelpRes grant in Ireland. They study the diversity and resilience of kelp ecosystems.

“We’re defining ‘resilience’ in this case as ‘the ability of an ecosystem to recover and maintain function,’” says Schoenrock-Rossiter.

Kelp forests are submerged marine algae, Schoenrock-Rossiter explains, and they are generally within the family of large brown algae seaweeds and in the order Laminariales. Although kelp may resemble an underwater plant, it is in fact a protist, the same family of organisms as molds and amoebas. Kelp forests are found on all continents except Antarctica, which is too cold for this kind of seaweed.?

Today’s discussion focuses on species within the Laminariales, which are dominant all over Europe, from the coast of Portugal to Svalbard and Greenland. They form a subsurface canopy. “Kelp forms this lovely kind of chaparral-like community, if we’re to compare it to the terrestrial ecosystem,” says Schoenrock-Rossiter. Laminariales are about three meters tall and very dense, dominating rocky shorelines with moderate exposure. They’re important ecosystem engineers, she says, meaning that they form a home and a food source for many species in the marine environment. They are sensitive abiotic and biotic stressors.?

Kelp Forest Stressors

Abiotic stressors include storms and climate change. The distribution of kelp forests has changed due to climate change, and it is predicted that it will continue to do so. Biological stressors include harvesting (wild or human) or overgrazing by herbivores, such as purple urchins, which decimate kelp forests along the northern coast of Norway. Kelp forests can recover from these kinds of events as urchins die off, but damage can occur quickly, and it can be devastating to local fisheries, coastal protection, and more.?

KelpRes

The study species of KelpRes is L. hyperborea, known in Ireland as “cuvie” or “mayweed.” It is generally in the subtidal region, and can live between 10-15 years. The species is unique in that it can be aged like a tree: prolonged winter stages create bands on the kelp similar to that of tree rings. Thus far, the oldest specimen Schoenrock-Rossiter’s team has found in Ireland is 15 years old, while others up to 18 years old have been located in Norway. As such, these individuals have the potential to structure ecosystems for a relatively long duration of time. Like all brown algae within the Laminariales family, says Schoenrock-Rossiter, they have a complex lifecycle.

L. hyperborea Lifecycle Stages

L. hyperborea’s sporophyte stage is what Schoenrock-Rossiter’s team considers the kelp.

• Structures ecosystem in this macroscopic form
• Diploid (has two pairs of chromosomes), and forms reproductive structures on its blade, where meiosis occurs in producing the haploids of single chromosomes and set spores
• Spores are mobile but microscopic; don’t travel very far in strong currents. Move around for about 24 hours, then settle out onto the benthic environment (such as bedrock stones and other structures)
• Spores develop into either male or female gametophytes, which produce gametes that recombine sexually to form a sporophyte.?
• A fertilization event allows recruitment of the sporophyte, which creates a macroscopic forest, theoretically the following year.

The kelp has a fairly complicated life cycle, says Schoenrock-Rossiter, with two crucial stages, macroscopic-microscopic. This is a seasonal pattern, such that these different lifecycle events occur on a seasonal scale:?

• Zoospore formation occurs in the winter
• Gametophyte development occurs in winter and spring
• New sporophyte generation starts in spring and continues through summer

Other species tend to start this process from early summer through autumn, so it’s clearer for the researchers to identify which species are recruiting and developing in the ecosystem.?

L. hyperborea Range Restrictions

This species has experienced past range restrictions.?

• In the last glacial maximum, it is projected to have retracted its range all the way down to the southern Irish coast, the southern UK, Brittany, and Portugal down to Morocco.?
• Currently, the kelp is distributed from the northern portion of the Portuguese coastline up to Svalbard (Norway). The most extreme projections from the Representative Concentration Pathway (RCP) and the Intergovernmental Panel on Climate Change (IPCC) predict that the species will retract northward all the way up to the mid-UK and southern Irish coastline.?

As such, climate change is a significant threat to this cold water kelp species.?

KelpRes’ Focus

Schoenrock-Rossiter’s research is interested in where the kelp has been found in Ireland specifically, as the government attempts to manage this resource on a national scale. Focus questions are:

1. Where have L. hyperborea ecosystems historically been found in Ireland??
2. What has L. hyperborea been used for by humans??
3. How has it been observed and recorded in the past??
4. How are people interacting with this species?
5. What is the genetic structure and connectivity across habitats in Ireland?
6. Is there genetic diversity within the populations??
7. What is the genetic structure in connectivity across populations within Ireland?
8. Is there natural resilience in the lifecycle of L. hyperborea (i.e. from macroscopic to microscopic stages)?
9. How can these habitats continue to be monitored moving forward to keep tabs on kelp forest presence, ecosystem health, and distribution shifts?

The History of Kelp in Ireland

It has been challenging to source historical data about kelp presence and health in Ireland, since kelp are very large and difficult to preserve. Even in old textbooks and scientific records, there is sparing data on subtidal species. The earliest record of hyperborea is from 1913 in Wexford County on Hook Head Peninsula. Records intermittently appear throughout the 1900s, stemming from a research project called Biomark.?

In the 2000s, a citizen science group, Sea Search Ireland, was founded with the purpose of expanding recordings of kelp observations. Schoenrock-Rossiter attributes recent progress in the understanding of kelp distribution to the development of technology like scuba diving and the internet, with its data-sharing capabilities. However, in the case of many citizen-run sites, the data is rarely updated, so kelp presence may be recorded once, but there is no further information on whether the kelp was alive at the time, ongoing ecosystem health, or even whether the ecosystem is still present.

From the perspective of cultural history, it’s well established that kelp has played an important role in Ireland agriculturally and economically.

Hotspots for recording kelp are typically centered around institutes of higher education, such as in Galway and Cork. This creates somewhat of a bias in datasets, which could be addressed by expanding research across the coastline.?

Monitoring Kelp ?

For the past five years, Schoenrock-Rossiter and her team have been working to create a modern baseline for kelp forest ecology in Ireland, create monitoring tools, contribute data to international networks, and ultimately develop long-term datasets to help understand and define the resilience of kelp habitats.?

To accomplish these goals, the team established monitoring locations with subsurface buoys that wouldn’t be disturbed by fishermen, which they have had difficulty maintaining so far.? KelpRes team have placed data loggers to record environmental conditions that are found within kelp forests, which will support modeling efforts. As part of current research efforts, the KelpRes team:

• Monitors recruitment habitats to determine what species preferentially settle into the ecosystems
• Observes succession processes, i.e. how kelp forests recover
• Conducts biodiversity transects, counting all organisms that are found in a certain area of the kelp forests to help define what lives there seasonally/annually, at different depths, and in different locations
• Determines biomass and age of kelp forest
• Studies pigments
• Looks at proteins that will distribute into food webs in the near shore ecosystem
• Observes growth rate to determine how biomass is produced and rate of production across the system

The KelpRes team has also looked at nearshore ecosystems to gain an understanding of the importance of kelp forests. In comparing kelp forests to reefs and rocky bottoms, the KelpRes team has found kelp forests to be quite unique. Each habitat is defined by the biological community associated with it. Even within kelp forests, different parts of the forests exhibit specific genetic characteristics and growth rates, allowing for unique kelp forest development.?

Species That Define a Kelp Forest

Certain species define kelp forests, and may indicate healthy kelp ecosystems, such as:

• Blue-rayed limpet, which selectively recruits two kelp species (L. digitata and L. hyperborea) and is generally found at the base of the blade from spring to summer
• Sea stars
• Sea cucumbers
• Common sea urchinsGastropods
• Filter feeders, which suggest they’re processing kelp organic carbon
• Certain commercial species, including lobsters and juvenile cod (Gadidae spp.)

Kelp Productivity and Agricultural Impacts

The highest kelp density corresponds to the highest calorie density. Harvesting kelp is an existing commercial industry in France and Norway, and is becoming increasingly so in Ireland. Highest density is found in shallower depths and stonier regions, 2-4 meters. This is where older individuals and communities are found, potentially implying that they’re more stable at those depths. As in terrestrial forests, where there are old specimens, the density of individuals decreases due to the canopy shading effect.?

KelpRes Tools

Stacy Krueger-Hadfield, PhD, Assistant Professor, University of Alabama at Birmingham has worked with the KelpRes team in Ireland for four years to define genetic diversity and structure in the kelp communities. Her tools are called “microsatellites,” which are repetitive regions across the genome that were previously used in paternity analysis. Microsatellites are polymorphic in variable regions across the genome, similar to what are used for 23andMe or similar ancestry sites. Using the same principles, Krueger-Hadfield is able to determine the structure and connectivity of the organism.

Popular genetic literature has increasingly revealed the importance of temporal sampling for understanding the resilience of populations and changes to genetic diversity. In terms of seaweed agriculture, there is little information available comparing kelp versus a land crop like corn in terms of productivity.?

Thus far, statistical evidence suggests a strong relationship between genetic differentiation and geographic distance. The greater the distance between populations, the greater the genetic distinction. These analyses don’t assume what’s going on in the populations, but can provide a great deal of information about genetic diversity and structure. The implication that macroalgae diversity is highly structured based on location has important management and conservation implications.?

Studying Succession, i.e. Kelp Community Recovery

In order to study how kelp communities recover from a major disturbance, termed “succession,” Schoenrock-Rossiter and her team observed a native succession plots. This means that they cleared a plot of bedrock, coral, and algae, and scraped off all the invertebrates and visible seaweed and monitored recovery. They also created a sterile succession plot: a concrete slab conditioned in seawater, and observed how each plot recovered over time.?

Native plot:

• After 100 days, juvenile kelps established
• After 208 days, kelps start to thin and get larger

Sterile plot:

• After 40 days, a biofilm turf community has begun building up (microscopic or filamentous algae), but no kelp
• By 115 days, invertebrate recruitment has begun, such as calcified worms, tunicates, and sponges
• After a full year, kelps begin showing up, indicating that there has been opportunity for kelps to produce spores from the sporophyte, settle and produce gametophyte, then recombine and produce juvenile sporophytes

The trajectory of the sterile plot indicates that there is a microscopic bank of kelp stages already present on bedrock. The KelpRes project aims to see how this relates to kelp ecosystem resilience. In order to do so, the team took a three-pronged approach:

1. Placed settlement tiles. These are cement blocks that held microscope slide racks left for a full year in natural conditions. The team took some of them out seasonally to capture seasonal reproduction. They also counted gametophytes, zoosopheres, and anything settling seasonally and annually.
2. Removed bedrock from kelp forests and attempted to grow kelp in an aquarium system that mimicked environmental conditions. They thought if they removed the canopy, microscopic things might grow quickly in the artificial environment.
3. Barcoded and metabarcoded both bedrock samples and microscope slides from seasonal and annual experiments to determine what could be found in the microscopic boundary layer. It isn’t possible to differentiate species of kelp based on microscopic stages, so barcoding can provide information about what the species might be.

Additionally, the team has bolstered citizen science efforts, so that divers can contribute records via an online submission platform.

Finding a Cost-Effective Way to Monitor Kelp Forests: Remote Sensing and Machine Learning

The rugosity of the coastline, with regular storms and extraordinary rockiness, creates challenges for cost-effective monitoring and mapping. As such, the KelpRes team began exploring the availability of satellite imagery, of which there is a substantial amount. Irish weather complicates satellites’ observation abilities, both in terms of visibility and resolution. As such, methods that work in places such as California are not applicable to the Irish context. Fortunately, Planet Labs, a remote sensing and imaging company, has pioneered the use of CubeSat, a small spacecraft launched in fleets of 2-300, which pass overhead 2-3 times a day and is able to capture images in high enough resolution to suit the KelpRes team’s needs.?

Additionally, the Irish government’s Geological Survey of Ireland and the Marine Institute have been mapping the country’s seabed from the coast to the deep Atlantic, which has been invaluable for KelpRes. Adam Golden, PhD, College Lecturer at National University of Ireland Galway is able to take data from CubeSat and overlay the bathymetry, emulating a dive one might take to the monitoring sites. KelpRes has been able to survey the kelp using CubeSat datasets, to the extent that they’re able to put constraints on where the kelp is located. The team can then apply some straightforward machine learning algorithms to locate kelp, and have found the process to be strikingly accurate. Thanks to this innovative class of remote sensing, it is feasible to monitor the kelp from orbit. Planet Labs is working to produce a generation of CubeSat with new spectrum paths, enabling them to see greater depths into the water.?

“You can use some very cool, dark arts in machine learning to take the data that we can work with at a high resolution here, and roll it back on to data taken with the Landsat spacecraft,” says Golden, referring to a spacecraft that has collected a great deal of data at lower resolution than is usable to the KelpRes team. “We have like 30 years of data or more from the Landsat program. We don't have the resolution, and we have spotty coverage. If we can ground-truth everything right now, we can go back in time, and to some extent we can track the predictions of how the kelp is gonna respond to the rising temperature in the actual ocean.”

Governance and Legislation of Kelp Forests in Ireland

There are currently no regulations related to kelp ecosystems, though there are for fisheries and near-shore ecosystems. Governance like the water framework directive and marine strategy framework directive does include text on good environmental or ecosystem status within nearshore habitats.

Moving forward, KelpRes is part of a global report on kelp ecosystem health. Schoenrock-Rossiter is hopeful that with the EU’S Green New Deal, kelp ecosystems will get more attention, as they aren’t currently as well-protected as they could be. KelpRes is working with the Environmental Protection Agency and National Park Service in Ireland to invest in more coastal and subtidal monitoring.?