Marine Ecological Processes Research Articles

First release of the Pelagic Size Structure database: global datasets of marine size spectra obtained from plankton imaging devices

Abstract. In marine ecosystems, most physiological, ecological, or physical processes are size dependent. These include metabolic rates, the uptake of carbon and other nutrients, swimming and sinking velocities, and trophic interactions, which eventually determine the stocks of commercial species, as well as biogeochemical cycles and carbon sequestration. As such, broad-scale observations of plankton size distribution are important indicators of the general functioning and state of pelagic ecosystems under anthropogenic pressures. Here, we present the first global datasets of the Pelagic Size Structure database (PSSdb), generated from plankton imaging devices. This release includes the bulk particle normalized biovolume size spectrum (NBSS) and the bulk particle size distribution (PSD), along with their related parameters (slope, intercept, and R2) measured within the epipelagic layer (0–200 m) by three imaging sensors: the Imaging FlowCytobot (IFCB), the Underwater Vision Profiler (UVP), and benchtop scanners. Collectively, these instruments effectively image organisms and detrital material in the 7–10 000 µm size range. A total of 92 472 IFCB samples, 3068 UVP profiles, and 2411 scans passed our quality control and were standardized to produce consistent instrument-specific size spectra averaged to 1° × 1° latitude and longitude and by year and month. Our instrument-specific datasets span most major ocean basins, except for the IFCB datasets we have ingested, which were exclusively collected in northern latitudes, and cover decadal time periods (2013–2022 for IFCB, 2008–2021 for UVP, and 1996–2022 for scanners), allowing for a further assessment of the pelagic size spectrum in space and time. The datasets that constitute PSSdb's first release are available at https://doi.org/10.5281/zenodo.11050013 (Dugenne et al., 2024b). In addition, future updates to these data products can be accessed at https://doi.org/10.5281/zenodo.7998799.

A laboratory study of the increasing competitiveness of Karenia mikimotoi under rising CO2 scenario

Ocean acidification (OA) driven by elevated carbon dioxide (CO2) levels is expected to disturb marine ecological processes, including the formation and control of harmful algal blooms (HABs). In this study, the effects of rising CO2 on the allelopathic effects of macroalgae Ulva pertusa to a toxic dinoflagellate Karenia mikimotoi were investigated. It was found that high level of CO2 (1000 ppmv) promoted the competitive growth of K. mikimotoi compared to the group of present ambient CO2 level (420ppmv), with the number of algal cell increased from 32.2 × 104 cells/mL to 36.75 × 104 cells/mL after 96 h mono-culture. Additionally, rising CO2 level weakened allelopathic effects of U. pertusa on K. mikimotoi, as demonstrated by the decreased inhibition rate (50.6 % under the original condition VS 34.3 % under the acidified condition after 96 h co-culture) and the decreased reactive oxygen species (ROS) level, malondialdehyde (MDA) content, antioxidant enzymes activity (superoxide dismutase (SOD), peroxidase (POD), glutathione peroxidase (GPX), glutathione reductase (GR) and catalase (CAT) and non-enzymatic antioxidants (glutathione (GSH) and ascorbic acid (ascorbate, vitamin C). Indicators for cell apoptosis of K. mikimotoi including decreased caspase-3 and -9 protease activity were observed when the co-cultured systems were under rising CO2 exposure. Furthermore, high CO2 level disturbed fatty acid synthesis in U. pertusa and significantly decreased the contents of fatty acids with allelopathy, resulting in the allelopathy weakening of U. pertusa. Collectively, rising CO2 level promoted the growth of K. mikimotoi and weakened allelopathic effects of U. pertusa on K. mikimotoi, indicating the increased difficulties in controlling K. mikimotoi using macroalgae in the future.

Direct Analysis of Marine Dissolved Organic Matter Using LC-FT-ICR MS.

Marine dissolved organic matter (DOM) is an important component of the global carbon cycle, yet its intricate composition and the sea salt matrix pose major challenges for chemical analysis. We introduce a direct injection, reversed-phase liquid chromatography ultrahigh resolution mass spectrometry approach to analyze marine DOM without the need for solid-phase extraction. Effective separation of salt and DOM is achieved with a large chromatographic column and an extended isocratic aqueous step. Postcolumn dilution of the sample flow with buffer-free solvents and implementing a counter gradient reduced salt buildup in the ion source and resulted in excellent repeatability. With this method, over 5,500 unique molecular formulas were detected from just 5.5 nmol carbon in 100 μL of filtered Arctic Ocean seawater. We observed a highly linear detector response for variable sample carbon concentrations and a high robustness against the salt matrix. Compared to solid-phase extracted DOM, our direct injection method demonstrated superior sensitivity for heteroatom-containing DOM. The direct analysis of seawater offers fast and simple sample preparation and avoids fractionation introduced by extraction. The method facilitates studies in environments, where only minimal sample volume is available e.g. in marine sediment pore water, ice cores, or permafrost soil solution. The small volume requirement also supports higher spatial (e.g., in soils) or temporal sample resolution (e.g., in culture experiments). Chromatographic separation adds further chemical information to molecular formulas, enhancing our understanding of marine biogeochemistry, chemodiversity, and ecological processes.

Long-term trends in functional diversity of exploited marine fish in the Azores’ archipelago: past and present

IntroductionEffective fisheries management requires monitoring and quantifying changes in exploited fish communities. Concerns about global fisheries sustainability have led to innovative approaches. Functional diversity, rooted in ecological theory, offers valuable insights into fishery activities and ecosystem processes. A trait-based approach was used to investigate the functional diversity of landed fish species in the Azores archipelago from 1980 to 2021.MethodsLandings data of exploited Actinopterygii and Elasmobranchii were provided by the Azores Fisheries Auction Services (LOTAÇOR/OKEANOS-UAc Fisheries Database). A trait matrix was built, incorporating 12 functional traits assigned to each species, capturing their importance in marine ecological processes. The Quickhull algorithm for convex hull was employed to calculate the volume occupied by the species in the four-dimensional functional space. Functional diversity (FD) was measured using three indices: functional richness (FRic), functional evenness (FEve), and functional divergence (FDiv). Trends in FD indices over the past 42 years were visualized using Generalized Additive Models (GAM) with interaction terms.Results and discussionGAM analysis revealed significant variations in the functional space and FD metrics over time. FRic exhibited peaks in the 1980s and 2010s, declining in the 1990s and from the 2010s onwards, indicating diversification in target species. The recent decrease in FRic can be attributed to the absence of catches of species with unique traits. The distribution of landings and trait combinations showed higher regularity in the functional space during the 1980s and 1990s (high FEve). Actinopterygii species targeted in the 1980s and 1990s had lower trait divergence (low FDiv) compared to those targeted from the 2000s onwards (high FDiv). Variability in FD can be linked to changes in fishing practices, species availability, market demand, environmental factors, and local regulations. This study underscores the importance of considering FD metrics alongside species richness and abundance when assessing the potential effects of fisheries on marine ecosystems and sustainable use of fishery resources.

Media bias on communicating conservation interventions: The case of large-scale marine protected areas in the South Atlantic

Since the Aichi Target 11 called for at least 10% of the world’s seas to be conserved through marine protected areas by 2020, there has been an increase in the creation of large-scale marine protected areas (LSMPAs). Despite advances made towards these area-based conservation targets, marine biodiversity continues declining globally, along with related decreases in ecosystem services provided to people. Thus, the challenge for the next decade is to improve the effectiveness of the already existing MPAs to safeguard marine biodiversity and ecological processes. Communication via mass media is a key strategy to advance marine conservation support from the public. Using media content analysis, we examined news on the implementation of LSMPAs in Brazil to understand message framing and to verify any mismatch between the content disclosed by mass media and the scientific community. We found that mass media coverage was mostly framed in an episodic way, with information focusing on specific isolated events (e.g., an increase in the percentage of MPA coverage). The media coverage did not address the gaps often raised by scientists in the design of the LSMPAs, thus mostly disclosing positive issues. Mass media can inform people whether to support or not to support conservation initiatives. Disclosing a broader picture of environmental issues is important not only to raise the public’s level of awareness about the conservation of the marine environment but also for achieving global biodiversity goals, ensuring the sustainable use of ocean resources and ultimately improve human well-being.

A robust, systematic approach for developing the biodiversity sector's input for multi-sector Marine Spatial Planning

As countries commit to developing their ocean-based economies sustainably, it is critical to secure the underlying marine biodiversity and ecological processes. Ecosystem-based Marine Spatial Planning (MSP) can support achieving this; however, because competition for ocean space is increasing, biodiversity prioritisation must be spatially efficient, conflict-averse, and robust to secure marine biodiversity appropriately. South Africa has a long history and real-world success in spatial planning on land; we aim to draw on this experience to develop an approach by which the biodiversity sector's input to MSP can be developed, in the context of MSP unfolding in South Africa. We used Marxan to develop the first National Coastal and Marine Map of Critical Biodiversity Areas (CBAs) and Ecological Support Areas (ESAs). There were 976 biodiversity features and design elements, and the cost layer aimed to avoid conflict with 19 sea-use sectors and avoid more heavily impacted areas. Biodiversity targets were met in 27.0% of the planning domain (5.4% Marine Protected Areas (MPAs), 21.6% CBAs), with 6.6% for ESAs. Sea-use guidelines were developed based on a matrix of activity compatibility with the management objective for CBAs (keep or restore to natural) and ESAs (avoid further degradation), with MPAs managed through their gazetted regulations. The CBA Map and sea-use guidelines formed the basis for the marine biodiversity sector plan for inclusion in MSP. This approach can be broadly applied, even with limited data, as the basis for multi-sector negotiations. We share seven recommendations from our experience to guide planners from other countries.

Correcting estimations of copepod volume from two‐dimensional images

AbstractAccurate plankton biomass estimations are essential to study marine ecological processes and biogeochemical cycles. This is particularly true for copepods, which dominate mesozooplankton. Such estimations can efficiently be computed from organism volume estimated from images. However, imaging devices only provide two‐dimensional (2D) projections of three‐dimensional objects. The classical procedures to retrieve volumes, based on the equivalent spherical diameter (ESD) or the best‐fitting ellipse, are biased. Here, we present a method to correct these biases. First, a new method aims to measure body area and fit an ellipse. Then, the body of copepods is modeled as an ellipsoid whose 2D silhouette is mathematically derived. Samples of copepod bodies are simulated with realistic shapes/sizes and random orientations. Their total volume is estimated from their silhouettes using the two classical methods and a correction factor is computed, relative to the known, total, volume. On real data, individual orientations and volumes are unknown but the correction factor still holds for the total volume of a large number of organisms. The correction is around −20% for the ESD method and + 10% for the ellipse method. When applied to a database of 150,000 images of copepods captured by the Underwater Vision Profiler, the corrections decreased the gap between the two methods by a factor of 54. In addition, the same procedure is used to evaluate the consequence of the bias in the estimation of individual volumes on the slopes of normalized biovolume size spectra and show that they are, fortunately, not sensitive to the bias.

Multiple biomarkers for indicating changes of the organic matter source over the last decades in the Min-Zhe sediment zone, the East China Sea

The temporal variation of sedimentary organic matters (SOM) in the East China Sea (ECS) is not fully assessed due to the complicated natural and anthropogenic processes. In this study, the compositions and distributions of multi-biomarker indicators (n-alkanes, n-alkanols and specific sterols) in a long sediment core collected from the Min-Zhe fined-grained sediment zone of the ECS were systematically studied to reveal variations of SOM sources and phytoplankton records over the last decades. The results of n-alkanes and sterols have demonstrated that terrestrial plants are the dominant SOM source, with the mean proportion of 67%. The temporal variation of terrestrial to marine biomarker ratios (TMBR) agree well with that of the dominant n-alkanes and terrigenous/aquatic ratios (TAR), suggesting that the multi-biomarker indicators yield a better assessment of the SOM source input. The regular variations of terrestrial OM and phytoplankton signals during the past decades record the interaction among marine ecological effects, anthropogenic activities and natural processes (i.e., extreme climate events). As a whole, the elevated productivity of marine phytoplankton since 1952 (mainly caused by enhanced nutrient inputs owing to the intensified human activities) and the decline in the period of 2005–2011 (likely influenced by the water impoundment of the Three Gorges Dam in 2003) were well reconstructed on the basis of brassicasterol (B) and dinosterol (D) indicators in this study. The B/(B + D) ratios also reveal the changes of community structure as a result of variations in the nutrient structure controlled by anthropogenic forcing. Notably, the anomalous peak in the abundance of n-alkanes with the even carbon predominance in about 1990 is identified for the first time, which may occur at that time of the first heavy rainfall after a long drought and is probably of the origin of biomass/fossil fuel combustion.

Rising CO2 will increase toxicity of marine dinoflagellate Alexandrium minutum

Ocean acidification caused by increasing emission of carbon dioxide (CO2) is expected to have profound impacts on marine ecological processes, including the formation and evolution of harmful algal blooms (HABs). We designed a set of experiments in the laboratory to examine the effects of increasing CO2 on the growth and toxicity of a toxic dinoflagellate Alexandrium minutum producing paralytic shellfish toxins (PSTs). It was found that high levels of CO2 (800 and 1200 ppm) significantly promoted the growth of A. minutum compared to the group (400 ppm) representing the current CO2 level. The total yields of PSTs by A. minutum, including both intracellular and extracellular toxins, were significantly enhanced, probably due to the induction of core enzyme activity and key amino acids synthesis for PST production. More interestingly, high level of CO2 promoted the transformation from gonyautoxin2&3 to gonyautoxin1&4 and depressed the release of PSTs from inside to outside of the cells. All these processes collectively led to an apparent increase of A. minutum toxicity. Our study demonstrated that rising CO2 would increase the risk of toxic A. minutum based on the comprehensive analyses of different processes including algal growth and toxin synthesis, transformation and release.

Changes in Coral Skeleton Growth Recorded by Density Band Stratigraphy, Crystalline Structure, and Hiatuses

Next-generation high resolution brightfield microscopy, x-radiography, and microcomputed tomography (microCT) analyses indicate that coral skeleton high density band (HDB) and low density band (LDB) stratigraphic sequences record dynamic changes in coral growth history. HDB-LDB sequences were studied within three small heads of Orbicella annularis, an ecological keystone species in the Caribbean Sea, collected from the leeward fringing reefs on Curaçao. Results indicate that HDB layers are formed by the thickening of exothecal and endothecal dissepiments, costae, and theca located at the margin and external to individual skeletal cups (corallites). Conversely, septa and columellas located inside individual corallites do not change in thickness. HDB-LDB stratigraphic sequences were laterally traced from the center to the margins of individual coral heads, demonstrating that shifts took place in the trajectory of coral skeleton growth. Normal HDB layers in the center of individual coral heads are formed at the same time (age-equivalent) as surfaces of erosion and no skeleton growth (hiatuses) on the margins of the heads. These hiatus surfaces within HDB-LDB stratal geometries indicate that multiple marine ecological and environmental processes affect the orientation, size, shape, and geometry of coral skeletons during coral growth history. The presence of these hiatus surfaces in other large coral heads would strongly impact sclerochronology and the interpretation of multiple environmental factors including sea surface temperature (SST).

Underwater Sound Levels in Glacier Bay During Reduced Vessel Traffic Due to the COVID-19 Pandemic

The global COVID-19 pandemic caused a sharp decline in vessel traffic in many areas around the world, including vessel-based tourism throughout Alaska, USA in 2020. Marine vessel traffic has long been known to affect the underwater acoustic environment with direct and indirect effects on marine ecological processes. Glacier Bay National Park in southeastern Alaska has monitored underwater sound since 2000. We used continuous, calibrated hydrophone recordings to examine 2020 ambient sound levels compared with previous years: 2018, the most recent year with data available, and 2016 for historical perspective. Park tourism occurs mainly in May–September. Overall, the number of vessel entries in Glacier Bay was 44–49% lower in 2020 (2020: n = 1,831; 2018: n = 3,599; 2016: n = 3,212) affecting all vessel classes, including the complete absence of cruise ships and only three tour vessel trips. In all years, we found clear seasonal and diurnal patterns in vessel generated noise, focused from 06:00 to 20:00 local time (LT) in the summer months. Broadband (17.8–8,910 Hz) sound levels in the 2020 Visitor Season were 2.7 dB lower than 2018 and 2.5 dB lower than 2016. Focusing on morning (06:00–09:00 LT) and afternoon (15:00–18:00 LT) time-blocks when tour vessels and cruise ships enter and exit Glacier Bay, median broadband sound levels were 3.3–5.1 dB lower in 2020 than prior years. At the 95th percentile levels, morning and afternoon peak times in 2020 were 6.3–9.0 dB quieter than previous years. A 3 dB decline in median sound level in the 125 Hz one-third octave band in 2020 reflects a change in medium and large vessel noise energy and/or harbor seal vocalizations. Our results suggest that all types of vessels had a role in the quieter underwater sound environment in 2020, with the combined acoustic footprint of tour vessels and cruise ships most evident in the decrease in the 95th percentile loudest sounds. This and other descriptions of the pandemic-induced quiet, and the gradual return to increased activity, can help inform efforts to improve existing methods to mitigate vessel noise impacts and maintain the ecological integrity of marine protected areas.

A preliminary investigation of marine litter pollution along Mandvi beach, Kachchh, Gujarat

Marine debris is a global issue with adverse impacts on marine organisms, ecological processes, aesthetics, and economies of nations. Several studies have been conducted to quantify the plastic debris along Indian beaches. This baseline study describes the results of a survey conducted on the types of plastic litters and their quantification during January to March 2020 along Mandvi beach in Gujarat. A quadrate having 10 × 10 m size was used for sampling the plastic litter on the shoreline. A total of 10 quadrates along the shore was considered for quantification of the plastic materials based on their density, color, and weight. The plastic material observed includes gutkha pouches, food wrappers, and fragments, along with plastic straws, cutleries, and fragments of various dimensions and thickness. The major contributing factors for the debris abundance in Mandvi beach are land-based sources and recreational activities. The results suggest that similar long-term projects covering extensive areas should be undertaken for accurate quantification of available debris and their impacts on coastal habitats of Gujarat.

Linking phytoplankton absorption to community composition in Chinese marginal seas

Phytoplankton pigments significantly affect photosynthesis and play a crucial role in regulating marine ecological and biogeochemical processes. Assessment of phytoplankton pigments through optical means is desirable as it may be extended to satellite remote sensing. Here, using an extensive data set of high performance liquid chromatography (HPLC) phytoplankton pigment concentrations and phytoplankton absorption spectra (aph(λ)) collected through five cruise surveys of the Chinese marginal seas during 2016 and 2017, we explore the potentials of using aph(λ) to estimate twenty pigments. Specifically, the first and second derivatives of aph(λ) are used to construct an aph(λ) - pigment model. The validation of the aph(λ)-derived pigment classes, specific to individual phytoplankton community and size groups, shows a generally satisfactory model performance. Additionally, hierarchical cluster analysis also exhibits high similarity within the classification results based on the measured and modeled pigments, where only two pigments were decided into different clusters. Although still preliminary in nature, this proof-of-concept study for the Chinese marginal seas shows the potentials of using satellite remote sensing to assess phytoplankton pigment composition once hyperspectral satellite data are available and aph(λ) inversion algorithms are developed and validated.

Synoptic relationships to estimate phytoplankton communities specific to sizes and species from satellite observations in coastal waters.

Knowing variations of phytoplankton community characteristics is of great significance to many marine ecological and biogeochemical processes in oceanography and related fields research. Satellite remote sensing provides the only viable path for continuously detecting phytoplankton community characteristics in the large-scale spatial areas. However, remote sensing approaches are currently hindered by limited understanding on reflectance responses to variations from phytoplankton community compositions and further do not achieve a true application by satellite observations. Here we analyze in situ observation data sets from three cruises in a dynamic marine environment covering those coastal water areas in the marginal seas of the Pacific Northwest (Bohai Sea, Yellow Sea, and East China Sea). The size/species-specific phytoplankton assemblages can be quantitatively defined by the high-performance liquid chromatography (HPLC)-derived phytoplankton pigments and customized diagnostic pigment analysis, as well as a matrix factorization "CHEMTAX" program. Therein, note that a suit of updated weight values for diagnostic pigments are proposed with better performance than others. The above-mentioned size/species-specific phytoplankton assemblages include three size classes, i.e., micro-, nano-, and picoplankton, and eight species typically existing in the investigated water areas. Relationship analysis illustrates us that relatively close and robust models can be established to associate three size-specific and four dominant species-specific phytoplankton biomasses with the total chlorophyll a. Those models are then applied to the Geostationary Ocean Color Imager (GOCI) images for the whole 2015 year, which generated annual mean distributions of size/species-specific phytoplankton biomasses. The current study represents a meaningful attempt to achieve the satellite remote-sensing retrievals on the phytoplankton community composition, especially the species-specific phytoplankton biomass in the study region.

A guide to the relationships between marine spatial patterns and ecological processes

Author(s): Wallingford, Piper D.; Pandori, Lauren L.M.; Bedgood, Samuel A.; Bracken, Matthew E.S.; Elsberry, Laura A.; Henry, Amy K.; Mahanes, Samuel A.; Sorte, Cascade J.B. | Abstract:

Hard-substrate habitats in the German Bight (South-Eastern North Sea) observed using drift videos

Comprehensive empirical data to inform benthic species distribution models for marine hard-substrate-dominated environments, are pivotal. However, such data are difficult to obtain. These data are crucial to the definition and demarcation of protected areas and for assessment of the ecological status and function of hard-substrate habitats.In this study, underwater video-observations of hard-substrate habitats within four target areas in the sand-dominated German Bight (SE North Sea) were investigated to obtain comprehensive information on hard-substrate distribution patterns, on the amount and sizes of stones and on the presence of sessile organisms.Based on three size classes (cobbles, boulders, large boulders) three hard-substrate distribution classes were identified: (1) widely scattered stones, (2) accumulations of stones and (3) dense stone fields. The ratios between cobbles, boulders and large boulders differed significantly between the investigated areas. Boulders and large boulders were largely colonized by sessile organisms, whereas cobbles in coastal areas were least frequently colonized. Physical disturbances of epibenthos resulting from abrasion and coverage by mobile sediments are discussed as a possible explanation for the proportional differences in the colonization of stones. Hard substrates in shallower, coastal areas appeared to be strongly influenced by sand abrasion because of higher current velocities and storm-induced waves. In deeper areas, located further offshore, disturbances caused by migrating sandy ripples mobilized by storm-events seemed to be more relevant.Habitat modelling of hard substrates and resultant ecological studies require sound information on the probability of epifaunal colonization for different substrate sizes, hard-substrate distribution patterns combined with hydrodynamic and physicochemical properties of the marine environment to produce valid results. We used a structured approach for the video-based analysis of hard-substrate habitats and present estimates of the colonization probability of differently-sized stones. Our study shows that the analysis of drift videos provides basic data at a suitable resolution to contribute to the monitoring and modelling of marine ecological processes.

In Situ and Satellite Observations of Phytoplankton Size Classes in the Entire Continental Shelf Sea, China

AbstractPhytoplankton size classes (PSCs) is of great significance for exploring marine ecological and biogeochemical processes. Remote sensing of PSCs has been successfully applied to open oceans; however, it is still quite limited for optically complex coastal oceans. In this study, the entire continental shelf sea of China including Bohai Sea (BS), Yellow Sea (YS), and East China Sea (ECS) characterized by distinctive turbid waters and impacted by plumes of large world‐class river (the Changjiang River) was taken as an example of turbid coastal ocean for remotely sensed spatial‐temporal distributions of PSCs. In situ data were collected from cruises during April to June in 2014 and an improved algorithm for PSCs retrieval was proposed. PSCs derived from GOCI (Geostationary Ocean Color Imager) images revealed that microplankton was dominant in the BS, the YS, and the nearshore ECS and nanoplankton distributed widely in the entire study area, while picoplankton mainly distributed in the offshore ECS in April, which was consistent with in situ investigation and related to environmental factors. Validation indicated that the improved algorithm provided a more accurate estimation of PSCs, with the root mean square error (RMSE) between estimated and measured size‐fractionated concentrations been 0.774, 0.257, and 0.142 mg m−3 for micro, nano, and picoplankton, respectively. Diurnal variations of PSCs were mainly affected by tidal currents and light intensity depending on different water types. These illustrated that remote sensed spatial distributions as well as diurnal variations of PSCs are effective in turbid continental shelf seas of China.

Remote‐Sensing Estimation of Phytoplankton Size Classes FromGOCISatellite Measurements in Bohai Sea and Yellow Sea

AbstractPhytoplankton size class (PSC), a measure of different phytoplankton functional and structural groups, is a key parameter to the understanding of many marine ecological and biogeochemical processes. In turbid waters where optical properties may be influenced by terrigenous discharge and nonphytoplankton water constituents, remote estimation of PSC is still a challenging task. Here based on measurements of phytoplankton diagnostic pigments, total chlorophylla, and spectral reflectance in turbid waters of Bohai Sea and Yellow Sea during summer 2015, a customized model is developed and validated to estimate PSC in the two semienclosed seas. Five diagnostic pigments determined through high‐performance liquid chromatography (HPLC) measurements are first used to produce weighting factors to model phytoplankton biomass (using total chlorophyllaas a surrogate) with relatively high accuracies. Then, a common method used to calculate contributions of microphytoplankton, nanophytoplankton, and picophytoplankton to the phytoplankton assemblage (i.e.,Fm,Fn, andFp) is customized using local HPLC and other data. Exponential functions are tuned to model the size‐specific chlorophyllaconcentrations (Cm,Cn, andCpfor microphytoplankton, nanophytoplankton, and picophytoplankton, respectively) with remote‐sensing reflectance (Rrs) and total chlorophyllaas the model inputs. Such a PSC model shows two improvements over previous models: (1) a practical strategy (i.e., modelCpandCnfirst, and then deriveCmasC‐Cp‐Cn) with an optimized spectral band (680 nm) forRrsas the model input; (2) local parameterization, including a local chlorophyllaalgorithm. The performance of the PSC model is validated using in situ data that were not used in the model development. Application of the PSC model to GOCI (Geostationary Ocean Color Imager) data leads to spatial and temporal distribution patterns of phytoplankton size classes (PSCs) that are consistent with results reported from field measurements by other researchers. While the applicability of the PSC model together with its parameterization to other optically complex regions and to other seasons is unknown, the findings of this study suggest that the approach to develop such a model may be extendable to other cases as long as local data are used to select the optimal band and to determine the model coefficients.

A regional correction model for satellite surface chlorophyll concentrations, based on measurements from sea water samples collected around Iceland

Near-surface chlorophyll a concentration is a fundamental component of marine ecological processes, and its changes reflect the phytoplankton growth (primary productivity as well as loss due to grazing and sinking) feeding into higher trophic levels. Time series of measurements from several satellite sensors since late 1997 can be used as a proxy of chlorophyll a concentrations after calibrating against direct sea water measurements from oceanographic surveys. Previous studies indicate a need for a regional correction model in specific ‘case 2’ areas, where the relationship between satellite measurements and in situ measurements is different from the relationship in the general ‘case 1’ areas, due to complex environmental characteristics in different areas. Subarctic and boreal North Atlantic, including the waters around Iceland, have been considered case 2 waters, but a regional correction model has not been developed until now. We collated all relevant measurements of near-surface chlorophyll a from sea water samples, available in the Marine Research Institute database, and matched by date and location with satellite chlorophyll records, i.e. the GSM CHL1 records offered by the GlobColour Project. A multiple linear regression model was fitted to the observed in situ chlorophyll measurements, based on the satellite chlorophyll values (CHL1) and physical covariates: day of the year, sun elevation, and ocean depth. The resulting parsimonious model converts the satellite measurements to estimates that are in much better agreement with in situ measurements (R2 increases from 0.2 to 0.5), and is therefore proposed for calibration of regional corrections to the GlobColour Project’s GSM chlorophyll parameter, CHL1.

Coexistence of urban uses and shellfish production in an upwelling-driven, highly productive marine environment: The case of the Ría de Vigo (Galicia, Spain)

The Ría de Vigo, located at the northern border of the Iberia-NW Africa eastern boundary upwelling ecosystem, is an incised deep (45 m maxim depth) valley originated by the combined action of tectonic and erosive processes. Upwelling events promote a quick renewal (3–4 days) of the volume of water in the Ría, which is replaced by cold, oxygenated and nutrient-rich subsurface oceanic water, giving rise to nutrient fertilization of the embayment that translates into high primary production rates (ca. 3 g C m−2 d−1). This high productivity allows the development of an important shellfish exploitation activity. The Ría de Vigo has 529 rafts where 37000 tons of mussels are produced annually. This territory has been subjected to an increasing human pressure since the early XX century deriving in an intense landscape transformation. The city of Vigo showed a six-fold increase in the number of inhabitants from 1900 to 2001 and more than 21% of the land in the study area is currently artificial. Therefore, urban and industrial activities coexist with local fisheries and shellfish mariculture that accounts for ca. 7% of the income and employment in this urban region. Incomplete depuration of wastewater in treatment plants, explain the relatively high contribution (22%) of sewage-derived nutrients to the total allochthonous fertilization in the Ría. Furthermore, and given the importance of shellfish production, microbial pollution originated from urban wastewater is considered as the main environmental threat of the Ría de Vigo. The dependence of the local economy on marine renewable resources together with the limitation of the natural productivity of the Rías imposed by anthropogenic pressure lies behind a significant fraction of the conflicts occurring in the region during the past two decades. The characteristics of Ría de Vigo, described in this review, confer this coastal ecosystem unique, conditions as a natural laboratory where the interaction between human activity and marine ecological processes can be studied within the framework of the World Harbour Project.