American Waters Research Articles

Population and Reproductive Dynamics of Zebra Mussels (Dreissena polymorpha) in Warm, Low-Latitude North American Waters.

AbstractZebra mussels (Dreissena polymorpha), first reported in Texas during 2009, have infested 28 Texas reservoirs over 11 years. This species has not previously invaded water bodies as warm as those in Texas, where temperatures approach or exceed its previously accepted incipient upper thermal limit of 30 °C, raising the question of how such temperatures impact its population dynamics. Over 3-5 years, monthly collections of mussels, sampling for planktonic mussel veligers, juvenile settlement data, and water quality parameters, were undertaken at Texas lakes Texoma, Ray Roberts, and Belton to estimate mussel shell length growth rates, life spans, reproductive periods, and settlement patterns. Biannual spawning periods occurred at water temperatures of 18 to 28 °C, resulting in distinct spring and fall juvenile settlement cohorts. Growth rates were rapid, with both cohorts attaining mean maximum shell lengths of 20-25 mm within 8-15 months of settlement, compared to European and northeastern US populations that attained similar sizes after 2-4 years. Shortened life spans were demarcated by adult mussel die-offs during summer months of elevated water temperature the year after initial settlement, leading to short-term cyclical fluctuations in population densities. Large-scale mussel die-offs were caused by flooding and hypoxia events. Elevated temperatures appeared to facilitate mussel invasiveness by increasing spawning frequency and elevating growth rates, thus reducing time to maturity and allowing population recovery within 1-2 years after environmentally induced severe population declines.

Radiological Investigation of Gas Embolism in the East Asian Finless Porpoise (Neophocaena asiaeorientalis sunameri)

Cetaceans have long been considered biologically adapted to suffer no adverse effects from diving-related tissue gas tension. However, increasing reports of gas embolism in cetaceans inhabiting European, Mediterranean and American waters have challenged the conventional understanding of marine mammal diving physiology. In human hyperbaric medicine, virtopsy techniques such as post-mortem computed tomography (PMCT) facilitate the visualization of gas embolism and could be performed adjunct to conventional autopsy. This research presents the first case of gas embolism identified in an East Asian finless porpoise inhabiting Asian waters. Massive gas embolic lesions were found in the liver, which had been compressing both the lungs and abdominal organs, and signs of pneumonia and parasitic infection were observed in both lungs. It is hypothesized that this porpoise might have been unable to expelin vivogas bubbles from its circulation due to pulmonary dysfunction. Consequently, gas bubbles agglomerated in the liver, resulting in the development of gas embolic lesions. The findings of the present study provide insights into the occurrence of gas embolism in the East Asian finless porpoise, highlighting the potential of PMCT as a promising tool for the diagnosis of gas embolism in stranded cetaceans.

Taxonomic re-appraisal for toothfish (Dissostichus: Notothenioidea) across the Antarctic Polar Front using genomic and morphological studies.

The Patagonian toothfish, Dissostichus eleginoides, is one of the largest predatory fishes inhabiting Southern Ocean waters spanning the Antarctic Polar Front (APF), a prominent biogeographic boundary restricting gene flow and driving species divergence between Antarctic and sub-Antarctic waters. In the light of emerging threats to toothfish conservation and sustainability, this study investigated genetic [mtDNA sequences and genome wide nuclear single nucleotide polymorphisms (SNPs)] and morphological data to critically evaluate the taxonomic status of toothfish north (Chile and Patagonian shelf) and south (South Georgia and South Sandwich Islands) of the APF. mtDNA revealed reciprocally monophyletic lineages on either side of the APF with coalescent analysis indicating these diverged during the Pleistocene. Integration with data from other sources suggests the Chilean/Patagonian lineage is endemic. SNP analysis confirmed restricted nuclear gene flow between both groups and revealed a consensus suite of positive outlier SNPs compatible with adaptive divergence between these groups. Finally, several morphological features permit unequivocal assignment of individuals to either of the clades. Based on the genetic, phenotypic and ecological divergence, the authors propose that toothfish on either side of the APF be recognised as distinct species, with the name D. eleginoides used for toothfish occurring in South American waters north of the APF and toothfish south of the APF being classified using the new name D. australis reflecting their southern distribution.

Assessment of organic substrates as sites for zebra mussel (Dreissena polymorpha) attachment in four West-Central Minnesota Lakes

Zebra mussels (Dreissena polymorpha) are an aquatic invasive species generalist with known ecological and economic impacts due to their settlement and attachment characteristics as well as their filtration abilities. Although zebra mussel attachment to abiotic substrates has been extensively studied, the importance of organic substrates for established zebra mussel populations in North American waters has not been evaluated. We assessed organic substrates in four west-central Minnesota lakes. Using qualitative analysis, we found most substrates were used proportionally to their availability. A quantitative assessment revealed significantly more zebra mussels attached to detritus than pondweeds (P < 0.05). Algae (filamentous and Chara spp.) were a significant suitable substrate for zebra mussel attachment (P < 0.05). Furthermore, more juvenile zebra mussels were found on organic substrates than were adults (P < 0.001). Although not always a consistent substrate, biological material as a vector for zebra mussel spread and settlement should be considered in further research to mitigate subsequent invasions and manage already naturalized populations.

Mini review: Characteristics of upwelling in several coastal areas in the world

This paper provides an overview of the upwelling processes and the controlling factors as an effort to reveal the characteristics and the intensities of upwelling events in several parts of the world. This review aimed at identifying the characteristics of upwelling and how the global climate controlling this physic phenomenon such as ENSO, IOD and Kelvin Wave. Several places in the Southeast Asia experienced high intensities of upwelling when El Nino events such as in South of Java, East Coast of Malaysia Peninsula and in Vietnam Coastal area. The results of this review found that area with the most intensive and productive upwelling in the world is South American waters and Banguela Upwelling System (BUS) in the African Coast. However, several other areas also show intensive and high productivity of upwelling, such as off the southern coast of Java Island in Indonesia and the Banda Sea and its surroundings. It is found that upwelling with stronger intensity can result in increase of mortality of certain organisms such as scallops. Additionally, increase of nutrients in a waters is often accompanied by an increase in several species of toxic algae that are harmful to the local fishery system (harmful algae blooms, HABs).

A new species of freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from Southern Brazil

The freshwater amphipod of the genus Hyalella is typical from continental American waters and shows high levels of endemicity and Brazil has the second largest diversity. A new species is described here, Hyalella longipropodus n. sp. that occurs in a spring of southern Brazil in the municipality of Palmeira das Misses, in the northwestern region of state of Rio Grande do Sul, southern Brasil. Hyalella longipropodus n. sp. shows the following character states: antenna 2 more than half body length, gnathopod 2 propodus elongated, uropod 1 inner ramus of male without apical curved setae, uropod 3 peduncle with seven strong distal setae with accessory setae, ramus of uropod 3 with ten cuspidate setae with accessory setae. Hyalella longipropodus n. sp. occurs in sympatry with H. gauchensis, but these differ especially in the size and shape of gnathopod 2, the presence of curved setae on uropod 1 in H. gauchensis and the absence in H. longipropodus n. sp., antenna length (longer in H. longipropodus n. sp.) and number of cuspidate setae on uropods 1, 2, and 3. Besides the morphological differences, H. longipropodus n. sp. presented genetic differences always above 19% for the COI gene and 29 % for the 16S rRNA gene, when compared with other species found in the northwestern region of the state of Rio Grande do Sul, showing that it is really a species not yet described by science.

Spatial Distribution Patterns of Appendicularians in the Drake Passage: Potential Indicators of Water Masses?

Appendicularians are one of the most common animals found within zooplankton assemblages. They play a very important role as filter feeders but are, unfortunately, inconsistently reported in the Antarctic literature. The present paper attempts to describe the zonal diversity of appendicularians and the main environmental factors influencing their communities in the Drake Passage. Samples were collected during Antarctic summer in 2009–2010. A total of eight species of larvaceans were identified. Fritillaria borealis was the species found in the highest numbers in almost the entire studied area, and was observed at all sampling stations. The distributions of other taxa were limited to specific hydrological zones and hydrological conditions. F. fraudax and Oikopleura gaussica were typical of the areas between the Polar Front and the Subantarctic Front zones, and their distributions were significantly correlated with temperature and salinity, likely making them good indicator species. The F. fusiformis distribution was strictly related to South American waters. In summary, temperature was the strongest environmental factor influencing the larvacean community structure in the Drake Passage, and we also found that testing environmental factors on larvaceans as a whole group did not give entirely reliable results.

Setting the Context for Offshore Wind Development Effects on Fish and Fisheries

Changes to fisheries that result from offshore wind farm (OWF) installations may be considered good or bad depending on various stakeholders’ perspectives. OWFs can act as artificial reefs that may benefit secondary fish production, but such effects may also have ecological consequences. The fisheries exclusion effect that turns some OWFs into no-go areas, hence effectively no-take zones, could provide resource enhancements or redistribution. However, the displacement of fishing effort may have consequences to fisheries elsewhere. Changes in the sensory environment related to sound, as well as electromagnetic fields and physical alterations of current and wind wakes, may have as yet unknown impacts on fisheries resources. Understanding the interactions among effect type, OWF development phase, and spatiotemporal population dynamics of commercial and recreational species remains chal-lenging, exemplified by the commercial fishery lobster genus Homarus in European and North American waters. While knowledge of the interactions between resource species and OWFs is improving, there remain questions on the wider interaction between and consequences of OWFs and fisheries. Studies of this wider relevance should aim to improve understanding of the economic and societal impacts of OWFs linked to ecosystem services that support fisheries. Furthermore, assisting fisheries management and providing advice requires monitoring and survey data collection at appropriate spatiotemporal scales. This information will help to determine whether OWFs have any meaningful impact on regional fisheries, and increased investments will be needed to target scientifically appropriate monitoring of OWFs and fisheries, which is supported by better integrated policy and regulation.

Reproductive biology of the finetooth shark (Carcharhinus isodon) in the northern Gulf of Mexico, with evidence of both annual and biennial reproduction

Intraspecific variability in life-history patterns is well documented in elasmobranchs, and defining regionally specific parameters is essential for proper management and sustainability of species. Studies on the reproductive biology of finetooth sharks (Carcharhinus isodon) have noted a potential disparity in periodicity within North American waters. To better define regional variability, the current study collected 1490 finetooth sharks (831 female, 659 male) from the northern Gulf of Mexico. The size-at-maturity was determined to be 995- and 961-mm fork length for females and males respectively. In males, the peak gonadosomatic index (GSI) in March and presence of semen in the seminal vesicles in April suggested spermatogenesis occurs from March to April. In females, ovulation occurred from May to June, with a peak GSI occurring in May and maximum vitellogenic follicle diameter occurring in May and June. Gestation was found to be 11–12 months, with parturition occurring in May and June and a mean brood size was 3.8±0.1 embryos. Of the 50 females examined during the ovulatory period, 32 exhibited annual and 18 exhibited biennial reproductive periodicity. The results from this study will be impactful, because regionally distinct reproductive parameters can now be considered for future assessments.

The Pathology of Cetacean Morbillivirus Infection and Comorbidities in Guiana Dolphins During an Unusual Mortality Event (Brazil, 2017–2018)

Cetacean morbillivirus (CeMV; Paramyxoviridae) is the most significant pathogen of cetaceans worldwide. The novel "multi-host" Guiana dolphin (Sotalia guianensis; GD)-CeMV strain is reported in South American waters and infects Guiana dolphins and southern right whales (Eubalaena australis). This study aimed to describe the pathologic findings, GD-CeMV viral antigen distribution and detection by RT-PCR (reverse transcriptase polymerase chain reaction), and infectious comorbidities in 29 Guiana dolphins that succumbed during an unusual mass-mortality event in Rio de Janeiro state, Brazil, between November 2017 and March 2018. The main gross findings were lack of ingesta, pulmonary edema, ascites, icterus, hepatic lipidosis, multicentric lymphadenomegaly, as well as pneumonia, polyserositis, and multiorgan vasculitis caused by Halocercus brasiliensis. Microscopically, the primary lesions were bronchointerstitial pneumonia and multicentric lymphoid depletion. The severity and extent of the lesions paralleled the distribution and intensity of morbilliviral antigen. For the first time in cetaceans, morbilliviral antigen was detected in salivary gland, optic nerve, heart, diaphragm, parietal and visceral epithelium of glomeruli, vulva, and thyroid gland. Viral antigen within circulating leukocytes suggested this as a mechanism of dissemination within the host. Comorbidities included disseminated toxoplasmosis, mycosis, ciliated protozoosis, and bacterial disease including brucellosis. These results provide strong evidence for GD-CeMV as the main cause of this unusual mass-mortality event.

Growth response of Dinophysis, Mesodinium, and Teleaulax cultures to temperature, irradiance, and salinity

Mixotrophic Dinophysis species threaten human health and coastal economies through the production of toxins which cause diarrhetic shellfish poisoning (DSP) in humans. Novel blooms of Dinophysis acuminata and Dinophysis ovum have occurred in North American waters in recent decades, resulting in the closure of shellfish harvesting. Understanding the ecology of Dinophysis species and their prey is essential to predicting and mitigating the impact of blooms of these dinoflagellates. The growth response of two new isolates of Dinophysis species, one isolate of Mesodinium rubrum, and two strains of Teleaulax amphioxeia were evaluated at a range of temperature, salinity, and irradiance treatments to identify possible environmental drivers of Dinophysis blooms in the Gulf of Mexico. Results showed optimal growth of T. amphioxeia and M. rubrum at 24 °C, salinity 30 – 34, and irradiances between 300 and 400 µmol quanta m − 2s − 1. Optimal Dinophysis growth was observed at salinity 22 and temperatures between 18 and 24 °C. Mesodinium and both Dinophysis responded differently to experimental treatments, which may be due to the suitability of prey and different handling of kleptochloroplasts. Dinophysis bloom onset may be initiated by warming surface waters between winter and spring in the Gulf of Mexico. Toxin profiles for these two North American isolates were distinct; Dinophysis acuminata produced okadaic acid, dinophysistoxin-1, and pectenotoxin-2 while D. ovum produced only okadaic acid. Toxin per cell for D. ovum was two orders of magnitude greater than D. acuminata. Phylogenies based on the cox1 and cob genes did not distinguish these two Dinophysis species within the D. acuminata complex.

New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods.

Nitrogen availability limits marine productivity across large ocean regions. Diazotrophs can supply new nitrogen to the marine environment via nitrogen (N2) fixation, relieving nitrogen limitation. The distributions of diazotrophs and N2 fixation have been hypothesized to be generally controlled by temperature, phosphorus, and iron availability in the global ocean. However, even in the North Atlantic where most research on diazotrophs and N2 fixation has taken place, environmental controls remain contentious. Here we measure diazotroph composition, abundance, and activity at high resolution using newly developed underway sampling and sensing techniques. We capture a diazotrophic community shift from Trichodesmium to UCYN-A between the oligotrophic, warm (25-29 °C) Sargasso Sea and relatively nutrient-enriched, cold (13-24 °C) subpolar and eastern American coastal waters. Meanwhile, N2 fixation rates measured in this study are among the highest ever recorded globally and show significant increase with phosphorus availability across the transition from the Gulf Stream into subpolar and coastal waters despite colder temperatures and higher nitrate concentrations. Transcriptional patterns in both Trichodesmium and UCYN-A indicate phosphorus stress in the subtropical gyre. Over this iron-replete transect spanning the western North Atlantic, our results suggest that temperature is the major factor controlling the diazotrophic community structure while phosphorous drives N2 fixation rates. Overall, the occurrence of record-high UCYN-A abundance and peak N2 fixation rates in the cold coastal region where nitrate concentrations are highest (~200 nM) challenges current paradigms on what drives the distribution of diazotrophs and N2 fixation.

Manajemen Pakan dan Analisis Usaha Budidaya Udang Vaname (Litopanaeus vannamei ) pada Lokasi yang Berbeda di Kabupaten Bangkalan dan Kabupaten Sidoarjo

Asian white shrimp or can be called vannamei shrimp has the Latin name Litopenaeus vannamei has native habitat in coastal waters and American sea waters. This research was carried out in September 2018 in the Asian white shrimp farming business unit Tanjung Putih Village Sepulu District Bangkalan District and in Penatar Sewu Village Tanggulangin District Sidoarjo Regency. This study population used 3 pond plots in Asian white shrimp culture in Tanjung Putih Village, Sepulu District, Bangkalan District and in Penatar Sewu Village Tanggulangin District Sidoarjo Regency. Sample size is determined from the amount of shrimp fry capacity stocked. The sampling technique was carried out by researchers by following activities in the field, census and visiting respondents directly on the farm or in the farmer's group home to obtain the information and data needed. The results showed that the best feed management was obtained the best results on the 4 sample ponds in Sidoarjo with an average final weight growth rate of 9.73 grams at the first partial harvest, 83% Feed Efficiency, and a 90% survival rate. As for the lowest feed management results obtained in sample ponds 1 Bangkalan with a yield of 6.98% growth, feed efficiency by 71% and survival rate of 86%. As for the results of the analysis of vannamei shrimp aquaculture business at different locations in Bangkalan and Sidoarjo districts, it was concluded that the best Production BEP was obtained in Sidoarjo's 4 sample ponds, amounting to 1427 kg. The best R / C ratio and Payback period is the average sample obtained in Sidoarjo. The conclusion of the best feed management and business analysis results is on the sidoajo sample ponds, the sidoarjo sample shows decent and efficient results.

Flathead Catfish (&lt;i&gt;Pylodictis olivaris&lt;/i&gt;) reproduction in Canada

Eleven Flathead Catfish (Pylodictis olivaris), representing at least five age classes, were collected between 2016 and 2018 in the lower Thames River, Ontario, Canada. The capture of two juveniles (total lengths 78 mm and 82 mm), the first records of juveniles in Canada, is a strong indication that reproduction has occurred. Previous records were thought to be individuals that dispersed from known populations in American waters of Lake Erie. Flathead Catfish is currently designated as data deficient by the Committee on the Status of Endangered Wildlife in Canada. These new findings may provide sufficient data to reconsider the conservation status of this species.

Updates on Ecology and Life Cycle of Sulcascaris sulcata (Nematoda: Anisakidae) in Mediterranean Grounds: Molecular Identification of Larvae Infecting Edible Scallops.

Sulcascaris sulcata is a nematode parasite of sea turtles, widespread in neritic foraging grounds with variable prevalence, reaching 30% in loggerhead turtles Caretta caretta feeding in northern Adriatic Sea. Ulcerative gastritis associated to high intensity of infection is reported in this host species. The life cycle of S. sulcata has been elucidated in Australian and American waters, demonstrating the ability of the species of infecting a wide range of intermediate hosts, represented by bivalve and gastropod molluscs. During regular sanitary inspections, nematode larvae were found within the adductor muscle of Pecten jacobeus and Aequipecten opercularis collected from the Northern Adriatic Sea. Morphological and molecular analyses were performed for the identification of larvae, and molecular data were obtained from adult S. sulcata as well. Analysis of the sequences of ITS fragment, and mitochondrial genes cox1 and cox2, revealed high genetic similarity among all the samples, and no geographical clustering was observed between adult parasites collected in Adriatic and Tyrrhenian Seas. A common allele pool was detected also between the two developmental stages, included larvae from Pecten and Aequipecten. The comparison with other members of the family Anisakidae demonstrated that S. sulcata formed a clear monophyletic cluster. This study reports the first identification of intermediate hosts for S. sulcata within the Mediterranean Sea. Infection in edible scallops justifies the exclusion of the product from the market and zoonotic potential of larvae of this anisakid nematode are yet to be completely excluded. Fidelity of sea turtles to selected foraging grounds, such as the Northern Adriatic shelf, warrants the life cycle of S. sulcata to perpetrate in the area; at the same time, long distance migrations of individuals justify the dispersal of infecting elements over the Mediterranean basin, regardless of turtles' origin.

Foraging rates of ram‐filtering North Atlantic right whales

Abstract North Atlantic right whales spend their summer months foraging primarily in American and Canadian Atlantic waters on high‐energy‐density prey. Here, they rapidly accumulate and store energy obtained within a few months to support future migrations and reproduction while fasting. High drag from their ram‐filter foraging strategy places a limit on what prey densities will be energetically efficient to target. Our understanding of the volume of prey‐laden water filtered by right whales during a dive or foraging bout, and what information they use to decide to forage or not, has been limited by the difficulties of measuring when they feed at depth, how fast they swim during continuous ram filtration and how often they might swallow accumulated prey. We used 10 DTAG deployments from right whales in the Bay of Fundy, Canada, to quantify swimming speeds and estimate the volume of prey‐laden water filtered per dive. We used the tag's inertial sensors to evaluate the timing of frequent biomechanical changes that likely indicate the truncation of continuous filtration, and whether the number or timing of these fluking bouts relates to longer feeding dives or other foraging decisions. During foraging dives, right whales descended at 1.4 (±0.2 SD) m/s and slowed to swim at 1.1 (±0.3) m/s while filtering. We found consistent pauses in the fluking behaviour of foraging right whales, every 56 (±22) s. Whales filtered on average 78 (±30) m3 of water per fluking bout and on average 673 (±201) m3 per dive. Right whales filter large volumes of water at low speeds with a high duty cycle, but require sufficiently high prey energy densities to compensate for a high‐drag foraging strategy. Closely related bowhead whales have a larger gape but swim more slowly, filtering greater volumes with lower drag. Our findings highlight that right whales acquire their energy in a relatively short period of intense foraging; even moderate changes in their feeding behaviour or their prey energy density are likely to negatively impact their yearly energy budgets and therefore reduce fitness substantially. A plain language summary is available for this article.

A new species and first record of Dracoderes (Kinorhyncha: Allomalorhagida: Dracoderidae) from American waters, with an identification key of the genus

A new species of Dracoderes, Daracoderes spyro sp. nov., is described from Hispaniola Island (Caribbean Sea), and represents the first record of this genus in American waters. The new species is distinguished from its congeners by the presence of lateroventral spines on segments 3–4 and 6–9, lateral accessory spines on segment 5, lateroventral tubes on segments 2, 5 and 10, and laterodorsal tubes on segment 8. Additionally, a dichotomous key to the species level for the genus Dracoderes is included.

First report of the family Zelinkaderidae (Kinorhyncha: Cyclorhagida) for the Caribbean Sea, with the description of a new species of Triodontoderes Sørensen & Rho, 2009 and an identification key for the family

A new species of Kinorhyncha, Triodontoderes lagahoo sp. nov., is described from Tobago Island, Caribbean Sea (western Atlantic Ocean) from a coastal, sandy habitat using both light and scanning electron microscopy. The species is characterized by the presence of middorsal acicular spines on segments 1–11 (that on segment 10 crenulated in males), laterodorsal crenulated spines on segment 10 only in males, lateroventral acicular spines on segments 3–4 and 6–8 (lateroventral spines also on segment 10 in females), lateroventral cuspidate spines on segments 5 and 9, lateral accessory acicular spines on segments 5 and 9, lateral accessory cuspidate spines on segment 8, ventrolateral acicular spines on segment 2 and ventrolateral cuspidate spines on segment 2. Females furthermore possess short papillae in ventrolateral position on segment 8 and ventromedial position on segment 9. The absence of cuspidate spines in lateral accessory position on segment 6 easily distinguishes T. lagahoo sp. nov. from the single known congener, Triodontoderes anulap. Moreover, also the arrangement of female papillae and sensory spots differ between the species. The finding of a new species of Triodontoderes in the Caribbean Sea is the first report of the genus for American waters and the Atlantic Ocean since its original description. Additionally, a dichotomous key for identification of the family Zelinkaderidae to species level, as well as systematic remarks on some morphological characters of the new species are included herein.

The effect of global climate change on the future distribution of economically important macroalgae (seaweeds) in the northwest Atlantic

An increase in greenhouse gas emissions has led to a rise in average global air and ocean temperatures. Increased sea surface temperatures can cause changes in species’ distributions, particularly those species close to their thermal tolerance limits. We use a bioclimate envelope approach to assess potential shifts in the range of marine macroalgae harvested in North American waters: rockweed ( Fucus vesiculosus Linnaeus, 1753), serrated wrack ( Fucus serratus Linnaeus, 1753), knotted wrack ( Ascophyllum nodosum (Linnaeus) Le Jolis, 1863), carrageen moss ( Chondrus crispus Stackhouse, 1797), and three kelp species ( Laminaria digitata (Hudson) J.V. Lamouroux, 1813; Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl et G.W. Saunders, 2006; and Saccharina longicruris (Bachelot de la Pylaie) Kuntze, 1891). We determined species’ thermal limits from the current sea surface temperatures associated with their geographical distributions. Future distributions were based on sea surface temperatures projected for the year ∼2100 by four atmosphere-ocean general circulation models and earth system models for regional concentration pathways (RCPs) 4.5 and 8.5. Future distributions based on RCP 8.5 indicate that the presence of all but rockweed ( F. vesiculosus) is likely to be threatened by warming waters in the Gulf of St. Lawrence and along the Atlantic coast of Nova Scotia. Range retractions of macroalgae will have significant ecological and economic effects including impacts on commercial fisheries and harvest rates and losses of floral and faunal biodiversity and production, and should be considered in the designation of marine protected areas.

Comparison of two atmospheric correction approaches applied to MODIS measurements over North American waters

Using in situ data of spectral remote sensing reflectance (Rrs, sr−1) collected over North American oceanic, coastal and estuarine waters between 2002 and 2016 (N = 942), we evaluate two atmospheric correction approaches applied to MODIS measurements. One is the POLYnomial based approach originally designed for MERIS (POLYMER) but adopted and implemented for MODIS, and the other is the traditional Gordon and Wang (1994b) near-infrared (NIR) approach with iteration to account for non-negligible NIR water-leaving radiance, which is currently embedded in the SeaWiFS Data Analysis System (SeaDAS) software package and used operationally by NASA for processing MODIS data (termed as NASA standard atmospheric correction or NSAC). The approaches are evaluated for both quality and quantity of their retrieved Rrs in the visible domain. The quality is gauged through three statistical measures between in situ and MODIS-retrieved Rrs: root mean square error (RMSE, sr−1), unbiased root mean square (uRMS), and mean bias (δ, sr−1). For common points where both approaches yield valid Rrs retrievals, POLYMER shows worse performance than NSAC for blue bands (<488 nm) and comparable performance for green and red bands. However, POLYMER shows the ability to retrieve more valid Rrs data points (2–3 folds) than NSAC for this evaluation dataset primarily because the latter fails over strong sun glint regions where the MODIS NIR bands saturate but the former is designed to work over sun glint regions using non-saturation MODIS bands. For those data points where only POLYMER yield valid Rrs retrievals, data quality is slightly worse than from the common data points. Although these results may vary slightly among individual subregions, it is generally true that POLYMER may be used as a surrogate of NSAC for atmospheric correction of MODIS when data quantity is significantly limited due to perturbations of sun glint and thin clouds that are typical for subtropical and tropical regions.