scholarly journals An Automated Method for Mapping Giant Kelp Canopy Dynamics from UAV

2021 ◽  
Vol 8 ◽  
Author(s):  
Katherine C. Cavanaugh ◽  
Kyle C. Cavanaugh ◽  
Tom W. Bell ◽  
Evan G. Hockridge
Keyword(s):  
Current Speed ◽  
Tidal Height ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Santa Barbara ◽  
Automated Method ◽  
Canopy Area ◽  
Satellite Sensors ◽  
Kelp Canopy ◽  
Abundance And Distribution

Satellite and aerial imagery have been used extensively for mapping the abundance and distribution of giant kelp (Macrocystis pyrifera) in southern California. There is now great potential for using unoccupied aerial vehicles (UAVs) to map kelp canopy at very high resolutions. However, tides and currents have been shown to affect the amount of floating kelp canopy on the water surface, and the impacts of these processes on remotely sensed kelp estimates in this region have not been fully quantified. UAVs were used to map fine-scale changes in canopy area due to tidal height and current speed at kelp forests off the coast of Palos Verdes, CA and Santa Barbara, CA. An automated method for detecting kelp canopy was developed that was 67% accurate using red-green-blue (RGB) UAV imagery and 93% accurate using multispectral UAV imagery across a range of weather, ocean, and illumination conditions. Increases in tidal height of 1 m reduced the amount of floating kelp canopy by 15% in Santa Barbara and by over 30% in Palos Verdes. The effect of current speed on visible kelp canopy was inconclusive, but there was a trend towards lower canopy area with increased current speed. Therefore, while tidal height and current speed can introduce significant variability to estimates of kelp abundance, the magnitude of this variability is site specific. Still, UAVs are a valuable tool for mapping of kelp canopy and can provide greater spatial resolution and temporal coverage than is possible from many satellite sensors. This data can provide insight into the patterns and drivers of high frequency fluctuations in kelp abundance.

scholarly journals Automated satellite remote sensing of giant kelp at the Falkland Islands (Islas Malvinas)

PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0257933
Author(s):  
Henry F. Houskeeper ◽  
Isaac S. Rosenthal ◽  
Katherine C. Cavanaugh ◽  
Camille Pawlak ◽  
Laura Trouille ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Satellite Imagery ◽  
Google Earth ◽  
Nitrate Content ◽  
Falkland Islands ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Canopy Area ◽  
Islas Malvinas

Giant kelp populations that support productive and diverse coastal ecosystems at temperate and subpolar latitudes of both hemispheres are vulnerable to changing climate conditions as well as direct human impacts. Observations of giant kelp forests are spatially and temporally uneven, with disproportionate coverage in the northern hemisphere, despite the size and comparable density of southern hemisphere kelp forests. Satellite imagery enables the mapping of existing and historical giant kelp populations in understudied regions, but automating the detection of giant kelp using satellite imagery requires approaches that are robust to the optical complexity of the shallow, nearshore environment. We present and compare two approaches for automating the detection of giant kelp in satellite datasets: one based on crowd sourcing of satellite imagery classifications and another based on a decision tree paired with a spectral unmixing algorithm (automated using Google Earth Engine). Both approaches are applied to satellite imagery (Landsat) of the Falkland Islands or Islas Malvinas (FLK), an archipelago in the southern Atlantic Ocean that supports expansive giant kelp ecosystems. The performance of each method is evaluated by comparing the automated classifications with a subset of expert-annotated imagery (8 images spanning the majority of our continuous timeseries, cumulatively covering over 2,700 km of coastline, and including all relevant sensors). Using the remote sensing approaches evaluated herein, we present the first continuous timeseries of giant kelp observations in the FLK region using Landsat imagery spanning over three decades. We do not detect evidence of long-term change in the FLK region, although we observe a recent decline in total canopy area from 2017–2021. Using a nitrate model based on nearby ocean state measurements obtained from ships and incorporating satellite sea surface temperature products, we find that the area of giant kelp forests in the FLK region is positively correlated with the nitrate content observed during the prior year. Our results indicate that giant kelp classifications using citizen science are approximately consistent with classifications based on a state-of-the-art automated spectral approach. Despite differences in accuracy and sensitivity, both approaches find high interannual variability that impedes the detection of potential long-term changes in giant kelp canopy area, although recent canopy area declines are notable and should continue to be monitored carefully.

scholarly journals Automated satellite remote sensing of giant kelp at the Falkland Islands (Islas Malvinas)

2021 ◽  
Author(s):  
Henry F. Houskeeper ◽  
Isaac S. Rosenthal ◽  
Katherine C. Cavanaugh ◽  
Camille Pawlak ◽  
Laura Trouille ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Satellite Imagery ◽  
Google Earth ◽  
Nitrate Content ◽  
Falkland Islands ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Canopy Area ◽  
Islas Malvinas

AbstractGiant kelp populations support productive and diverse coastal ecosystems in both hemispheres at temperate and subpolar latitudes but are vulnerable to changing climate conditions as well as direct human impacts. Observations of giant kelp forests are spatially and temporally patchy, with disproportionate coverage in the northern hemisphere, despite the size and comparable density of southern hemisphere kelp forests. Satellite imagery enables the mapping of existing and historical giant kelp populations in understudied regions, but automating the detection of giant kelp in large satellite datasets requires approaches that are robust to the optical complexity of the shallow, nearshore environment. We present and compare two approaches for automating the detection of giant kelp in satellite datasets: one based on crowd sourcing of satellite imagery classifications and another based on a decision tree paired with a spectral unmixing algorithm (automated using Google Earth Engine). Both approaches are applied to satellite imagery (Landsat) of the Falkland Islands or Islas Malvinas (FLK), an archipelago in the southern Atlantic Ocean that supports expansive giant kelp ecosystems. The performance of each method is evaluated by comparing the automated classifications with a subset of expert-annotated imagery cumulatively spanning over 2,700km of coastline. Using the remote sensing approaches evaluated herein, we present the first continuous timeseries of giant kelp observations in the FLK region using Landsat imagery spanning over three decades. We do not detect evidence of long-term change in the FLK region, although we observe a recent decline in total canopy area from 2017-2021. Using a nitrate model based on nearby ocean state measurements obtained from ships and incorporating satellite sea surface temperature products, we find that the area of giant kelp forests in the FLK region is positively correlated with the nitrate content observed during the prior year. Our results indicate that giant kelp classifications using citizen science are approximately consistent with classifications based on a state-of-the-art automated spectral approach. Despite differences in accuracy and sensitivity, both approaches find high interannual variability that impedes the detection of potential long-term changes in giant kelp canopy area, although recent canopy area declines are notable and should continue to be monitored carefully.

Mechanisms leading to recruitment inhibition of giant kelp Macrocystis pyrifera by an understory alga

2021 ◽  
Vol 657 ◽  
pp. 59-71
Author(s):  
BA Beckley ◽  
MS Edwards
Keyword(s):  
Field Experiments ◽  
Local Community ◽  
Kelp Forest ◽  
Macrocystis Pyrifera ◽  
Forest Recovery ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Combined Effects ◽  
Life Stages ◽  
Survival And Growth

The forest-forming giant kelp Macrocystis pyrifera and the communities it supports have been decreasing across their native ranges in many parts of the world. The sudden removal of giant kelp canopies by storms increases space and light for the colonization by understory macroalgae, such as Desmarestia herbacea, which can inhibit M. pyrifera recovery and alter local community composition. Understanding the mechanisms by which algae such as D. herbacea interact with M. pyrifera can provide insight into patterns of kelp forest recovery following these disturbances and can aid in predicting future community structure. This study experimentally tested the independent and combined effects of two likely competitive mechanisms by which D. herbacea might inhibit recovery of M. pyrifera in the Point Loma kelp forest in San Diego, California (USA). Specifically, we conducted field experiments to study the individual and combined effects of shade and scour by D. herbacea on the survival of M. pyrifera microscopic life stages, and the recruitment, survival, and growth of its young sporophytes. Our results show that scour had the strongest negative effect on the survival of M. pyrifera microscopic life stages and recruitment, but shade and scour both adversely affected survival and growth of these sporophytes as they grew larger. Canopy-removing storms are increasing in frequency and intensity, and this change could facilitate the rise of understory species, like D. herbacea, which might alter community succession and recovery of kelp forests.

scholarly journals Southward decrease in the protection of persistent giant kelp forests in the northeast Pacific

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Nur Arafeh-Dalmau ◽  
Kyle C. Cavanaugh ◽  
Hugh P. Possingham ◽  
Adrian Munguia-Vega ◽  
Gabriela Montaño-Moctezuma ◽  
...  
Keyword(s):  
Baja California ◽  
Marine Reserves ◽  
Fold Increase ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Central California ◽  
Northeast Pacific ◽  
The Face ◽  
High Resolution Satellite Imagery ◽  
Northeast Pacific Ocean

AbstractKelp forests are globally important and highly productive ecosystems, yet their persistence and protection in the face of climate change and human activity are poorly known. Here, we present a 35-year time series of high-resolution satellite imagery that maps the distribution and persistence of giant kelp (Macrocystis pyrifera) forests along ten degrees of latitude in the Northeast Pacific Ocean. We find that although 7.7% of giant kelp is protected by marine reserves, when accounting for persistence only 4% of kelp is present and protected. Protection of giant kelp decreases southerly from 20.9% in Central California, USA, to less than 1% in Baja California, Mexico, which likely exacerbates kelp vulnerability to marine heatwaves in Baja California. We suggest that a two-fold increase in the area of kelp protected by marine reserves is needed to fully protect persistent kelp forests and that conservation of climate-refugia in Baja California should be a priority.

The biology and ecology of giant kelp forests.

Phycologia ◽  
2016 ◽  
Vol 55 (1) ◽  
pp. 104-104
Author(s):  
John J. Bolton
Keyword(s):  
Kelp Forests ◽  
Giant Kelp

Bio-optimisation of a tidal channel

2020 ◽  
Author(s):  
Rory O'Hara Murray ◽  
Matthew Lewis
Keyword(s):  
Hydrodynamic Model ◽  
Kelp Forest ◽  
Three Dimensional ◽  
Electricity Consumption ◽  
Tidal Energy ◽  
Current Speed ◽  
Kelp Forests ◽  
Tidal Channel ◽  
Matthew Lewis ◽  
Tidal Stream

<p>Scotland has ambitious decarbonisation and climate change objectives, such as generating 100% of gross annual electricity consumption from renewable sources by 2020. Tidal stream energy is a renewable and predictable source of energy that converts the kinetic energy within tidal currents, into electricity, using a hydrokinetic device such as a horizontal axis turbine. However, economically viable tidal stream development is currently confined to areas of exceptionally high current speeds, and this can severely limit the choice of area. If the speed threshold required for an economically viable tidal site can be lowered then the number of potential sites could increase dramatically.</p><p>It is well known that macro-algae (e.g. kelp) grow in perspective tidal energy sites, as they requiring similar water depths and current speeds. Furthermore, kelp is known to grow in dense patches, reaching from the sea-floor to the ocean surface, and can modify tidal current speeds. Indeed, observations have shown that “kelp forests” can locally reduce current speeds by a third (Jackson and Winant, 1983). This local reduction in current speed will cause an increase in speed elsewhere, in order to conserve mass. Therefore, we hypothesise that by adding a kelp forest in the vicinity of a tidal channel, the current speed and tidal stream resource could be increased sufficiently for the site to become economical.</p><p>A three dimensional finite volume hydrodynamic model has been used to model an idealised tidal channel. The drag imposed by kelp was theoretically calculated and represented in the model as a sub grid scale momentum sink. The changes to the current speed resulting from this bio-optimisation of the tidal channel were investigated and show that the current speed in the centre of the channel can be increased. Kelp were then added to a previously developed hydrodynamic model of the Pentland Firth and Orkney Waters to investigate how such bio-optimisation could influence an area currently being considered for substantial tidal stream development. The changes on both the areas of suitable tidal stream development and the power yield are investigated.</p><p><strong>Acknowledgements</strong></p><p>Matthew Lewis wishes to thank Aaron Owen and Ade Fewings at SuperComputingWales, and Fearghal O'Donncha at IBM-research Ireland for fruitful discussions, and the METRIC grant, EP/R034664/1.</p><p><strong>References</strong></p><p>Jackson, G. A. and Winant, C. D. (1983). Effect of a kelp forest on coastal currents. Continental Shelf Research, 2(1), pp.75-80.</p>

scholarly journals Uneven protection of persistent giant kelp forest in the Northeast Pacific Ocean

2020 ◽  
Author(s):  
Nur Arafeh-Dalmau ◽  
Kyle Cavanaugh ◽  
Hugh Possingham ◽  
Adrian Munguia-Vega ◽  
Gabriela Montano-Moctezuma ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Kelp Forest ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Northeast Pacific ◽  
Habitat Dynamics ◽  
Climate Adaption ◽  
Northeast Pacific Ocean

In most regions, the distribution of marine forests and the efficacy of their protection is unknown. We mapped the persistence of giant kelp forests across ten degrees of latitude in the Northeast Pacific Ocean and found that 7.7% of giant kelp is fully protected, with decreasing percentages from north to south. Sustainability goals should prioritize kelp mapping and monitoring, while protection and climate adaption targets should account for habitat dynamics.

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