Macroalgal Diversity Research Articles

Marine Macroalgae Diversity at Bhuigaon Coast, District Palghar, Maharashtra

Marine Macroalgae Diversity at Bhuigaon Coast, District Palghar, Maharashtra

Species Composition and Distribution of Tropical Marine Macroalgae In The Pari Island Reef Cluster, Jakarta

The objective of this study was to analyze the species composition and distribution of marine macroalgae at Pari Island reef cluster-Seribu Islands reef system Jakarta based on specimen information available in Reference Collection of Research Center for Oceanography (RCO-LIPI). The Macroalgae specimens were collected irregularly by researchers during marine expedition projects from 1973 until 2014. Taxonomic identification of specimens was conducted in 2014, validation of species names was updated in May 2020 through www.macroalgaebase.org. The floristic composition value of macroalgae was analyzed using the C/P, R/P, and (R+C)/P ratio. Bray-Curtis similarity index analyzes were performed to visualize differences in macroalgae species from the different islands. We recorded a total of 41 species from 25 genus and 18 families. Rhodophyta represented the most significant number of taxa with 20 species (49%), followed by Chlorophyta with 11 species (27%) and Phaeophyta with ten species (24%). In this study, we found that Sargassum polycystum, Gracilaria salicornia, Amphiroa fragilisima, and Halimeda opuntia are dominant species in the study area. The highest macroalgae diversity found in Kongsi Island with 33 species, while the lower diversity found in Pari Island with five species. Bray-Curtis Similarity index showed that Kongsi Island and Burung Island have the highest similarity value with 29,26%, while Tikus Island and Pari Island have the lowest similarity value with 11,76%. The macroalgae distribution in the Pari island reef cluster influenced by the difference of substrate profile and environmental pressure derived from human activities. Proper management of macroalgae resources is necessary to preserve the sustainability of the macroalgae ecosystem. Keywords: macroalgae, composition, distribution, Pari Island

Nearshore ecosystems on seabird islands are potentially influenced by invasive predator eradications and environmental conditions: a case study at the Mercury Islands, New Zealand

Seabirds maintain island ecosystem function by providing rich marine-derived nutrients to the islands where they nest. These nutrients are returned to the sea through runoff, fertilizing the nearshore environment. Invasive predators disrupt this bottom-up control by decimating seabird populations. While invasive predator eradications lead to terrestrial recovery on seabird islands, there is little information on the nearshore impact. We determined how nearshore macroalgae communities and seabird-derived nitrogen concentrations are influenced by predator eradications and environmental parameters (sampling depth, season, wave exposure, and runoff). This case study examined 4 islands in the Mercury Islands archipelago, representing 3 eradication histories: never invaded by mammalian predators, eradicated over 30 yr ago, and eradicated 2 yr ago. Macroalgal diversity was highest at never-invaded islands, followed by islands in order of eradication year (eradicated 30 and 2 yr ago). The amount of seabird-derived nitrogen (δ15N) in algae was higher during the rainy season and decreased with sampling depth and wave exposure. Sampling near high runoff points resulted in increased δ15N in red algae alone. Never-invaded islands had the highest δ15N in most species. With species found at both eradicated islands, the recently eradicated island had unexpectedly higher δ15N than the island eradicated over 30 yr ago. This discrepancy may be a result of the recently eradicated island’s large size and presence of streams, estuaries, and sheltered bays. Studying nearshore habitats is crucial in understanding the extent to which seabirds act as a conduit of the land-sea interface and the marine impacts of island management.

Influence of monsoonal storm disturbance on the diversity of intertidal macroalgae along the eastern coast of Johor (Malaysia)

The effects of cyclical disturbances towards macroalgal community structure could reveal the progression of short-term colonisation but are understudied in tropical settings, especially in Malaysia. The storms associated with monsoon events modify the local macroalgal community structure, and this study aims to determine the variation in species, assemblage and cover of macroalgae during the monsoonal cycle of 2015 to 2016. Four locations (Pantai Pasir Lanun, Pulau Mawar, Telok Gorek and Tanjung Lompat) along the eastern coast of Johor were surveyed during the post-monsoon (January–April 2015), pre-monsoon (May–August 2015), monsoon (September–December 2015) and the beginning of the subsequent post-monsoon (January–February 2016) periods. Line transects (25 m) were deployed at the study sites, and along each line, square quadrats (50 × 50 cm) were placed alternately at every 1 m. These transects provided data on macroalgal cover, frequency and diversity indices. Overall, macroalgal species richness was highest at Tanjung Lompat (n = 31) and lowest at Pulau Mawar (n = 5). The physical disturbances associated with the storm event were most profound at Pantai Pasir Lanun and Pulau Mawar. Here, macroalgal cover reduced to 0% at the end of the monsoon period in December 2015. The highest Shannon index value was observed at Tanjung Lompat (1.54) and lowest at Telok Gorek (0.52). Comparisons between the monsoonal periods revealed that the highest Shannon index value was found during the pre-monsoon period of 2015 (up to 2.13) compared with the monsoon period of 2015 (up to 1.49). We report that the species Chaetomorpha spp. and Cladophoropsis membranacea played a dominant role as first-colonisers, appearing within 1 month from the onset of the post-monsoon period. This study suggests that despite a loss of local macroalgal diversity after storm events, natural re-establishment of the macroalgal community would ensue in cyclical patterns.

Current biodiversity of Mandapam group of Islands in Gulf of Mannar Marine Biosphere Reserve, Southeast coast of Tamil Nadu, India

The global climate change is known to involve in the decline of biodiversity from different ecosystems, including coral reefs worldwide. The spatial distribution of reef associated flora and fauna in the Gulf of Mannar (GoM) Marine Biosphere Reserve (GOMMBR) are declined due to damage of coral reefs by three major global problems observed in coral reefs, pertaining to frequent bleaching events, sedimentation and overwhelming algal communities. The occurrence of rich biodiversity in reef areas indicates the healthy condition of an iconic reef ecosystem. In this study, to assess the health status of coral reefs in Mandapam group of Islands under GoM, the diversity and distribution patterns of species composition assembled in reefs at seven Islands were analyzed. In 2019, summer temperature range was exceeded between 32 to 36 °C than usual range 28 to 30 °C, which resulted again massive coral bleaching in GoM. Statistical analysis revealed the high diversity of macroalgae in all the reef sites at Mandapam group Islands. Considerably, dead reefs in Mandapam group Islands represent 90% of algal communities and very less to scarce faunal diversity. While, faunal diversity was well diversified in the live coral cover areas and reefs with less macroalgal assemblage. This assessment provides current reef biodiversity data for gaining further insights into complex spatial distribution patterns of reef biota in GoM, and this will support the authorities to plan conservation efforts and to support livelihood of local fisher folk community.

Phycological Herbaria as a Useful Tool to Monitor Long-Term Changes of Macroalgae Diversity: Some Case Studies from the Mediterranean Sea

The Mediterranean Sea is currently experiencing a decline in the abundance of several key species, as a consequence of anthropogenic pressures (e.g., increase in human population, habitat modification and loss, pollution, coastal urbanization, overexploitation, introduction of non-indigenous species and climate change). Herbaria and natural history collections are certainly fundamental for taxonomic studies, but they are also an invaluable, if currently underestimated, resource for understanding ecological and evolutionary responses of species to environmental changes. Macroalgae herbarium collections, which are really consistent (ranging from 200,000 to approximately 500,000 specimens) in some European herbaria (e.g., Muséum National d’Histoire Naturelle in Paris, University of Copenhagen, Natural History Museum in Kensington), can be successfully used as real “witnesses” to biodiversity changes. In this respect, we report some case studies from the Mediterranean Sea which summarize well the potential of macroalgae herbarium specimens to provide useful data on biodiversity changes. Indeed, these data enable the evaluation of the responses of biota, including shifts in species ranges, the detection of the presence of introduced species, and the prediction of changes in species distributions and patterns under future climate scenarios. To increase the use of this invaluable tool of research, their curation, the digitization of collections, and specimen genomics should be even more addressed.

Correlation between macroalgae diversity and water quality in Southwest Maluku waters

Macroalgae play an important role in the ecosystem of the coastal area, serving as a shelter ground, nursery ground, and feeding ground. Macroalgae communities are directly influenced by water quality. This study aim was to determine the correlation between the macroalgae diversity and water quality in southwest Maluku waters. This research was conducted in September 2019 at seven research stations. Macroalgae samples were collected by transect method, while seawater quality was measured using Van Dorn Water Sampler. The macroalgae diversity, species composition, and dominance were determined. Water quality parameters analyzed were temperature, salinity, pH, phosphate, nitrate, and ammonia. Correlations between macroalgae diversity and water quality were determined using principal component analysis. This study recorded 45 species of macroalgae consisting of 15 species of red algae (Rhodophyta), 6 species of brown algae (Phaeophyta), and 24 species of green algae (Chlorophyta). Diversity Index varied ranged from low to moderate categories (0.969 - 2.345). Water quality in general is still quite good for macroalgae life. Macroalgae diversity and water quality correlate and influence each other.

Seaweeds through time: Morphological and ecological analysis of Proterozoic and early Paleozoic benthic macroalgae

Benthic marine macroalgae or seaweeds are key ecological players in oceans today and have been since the Proterozoic. To date, however, morphological and evolutionary patterns for Precambrian macroalgae have been documented only in rather broad terms. To refine our understanding in this critical interval, we updated a dataset of Proterozoic to early Paleozoic noncalcified macroalgal fossils preserved as macroscopic carbonaceous compressions. The data were analyzed using non-parametric multidimensional scaling (NMDS) and functional-form group (FFG) approaches, in order to characterize morphological and ecological evolutionary patterns of these macroalgae. At the broadest scale, the results show progressive increases in thallus size, morphospace range, and aspects of ecological complexity such as canopy heights, surface area/volume ratios, and functional-form groups through time. These trends, however, are not always monotonous. In particular, significant increases in Proterozoic macroalgal morphological diversity and maximum size appear to have occurred in the Neoproterozoic (Tonian and Ediacaran periods, respectively). Analysis of Ediacaran macroalgal assemblages shows that macroalgae broadly follow the Ediacara-like fossil assemblages, with a significant drop in most studied metrics in the terminal Ediacaran stage (~550–539 Ma). The latter event occurs during the Kotlinian crisis experienced by Ediacara-type macro-organisms, highlighting the possibility that this extinction event during the Ediacaran-Cambrian transition affected both macroalgae and Ediacara-type macro-organisms. Our analysis also confirms an Ordovician increase in the morphological and ecological diversity of macroalgae.

Application of multiplatform, multispectral remote sensors for mapping intertidal macroalgae: A comparative approach

Abstract Intertidal macroalgal communities are economically and ecologically important and, with a likely increase in anthropogenic pressures, there is need to evaluate and monitor these diverse habitats. Efforts to conserve and sustainably manage these habitats must be underpinned by accurate, cost‐effective, and efficient data collection methods. The high spatial and temporal resolution of unmanned aerial vehicles (UAVs), compared with satellites and aircraft, combined with the development of lightweight sensors, provides researchers with a valuable set of tools to research intertidal macroalgal communities. The ability of multispectral sensors, mounted on a satellite, an aircraft, and a UAV, to identify and accurately map the intertidal brown fucoid Ascophyllum nodosum (Fucales, Ochrophyta) at a site with a low species diversity of macroalgae were compared. Visual analysis confirmed that the spatial resolution of satellite imagery was too coarse to map intertidal macroalgae as it could not capture the fine spatial patterns of the macroalgal community. High‐resolution RGB (colour) imagery, taken during the aircraft and UAV surveys, was used to collect training and reference data through the visual identification and digital delineation of species. Classes were determined based on the level of taxonomic detail that could be observed, with higher levels of taxonomic detail observed in the UAV imagery over the aircraft imagery. Data from both were used to train a maximum‐likelihood classifier (MLC). The UAV imagery was able to more accurately classify a distinct A. nodosum class, along with other macroalgal and substratum classes (overall accuracy, OA, 92%), than the aerial imagery, which could only identify a lower taxonomic resolution of mixed A. nodosum and fucoid class, achieving a lower OA (78.9%). This study has demonstrated that in a coastal site with low macroalgal species diversity, and despite the spectral similarity of macroalgal species, UAV‐mounted multispectral sensors proved the most accurate for focused assessments of individual canopy‐forming species.

Long-term changes (1800–2019) in marine vegetational habitats: Insights from a historic industrialised coastal area

Macrophytes play an important structural and functional role in marine ecosystems but are experiencing a considerable decline in many areas of the Mediterranean Sea. Despite the long tradition of studies on vegetated marine habitats in the Gulf of Naples (Italy), a gap of knowledge on their long-term dynamics has recently been highlighted, mainly in the most anthropised areas. This work aimed to provide insights from the historic industrialised coastal area of the Site of National Interest (SIN) Bagnoli-Coroglio (Gulf of Pozzuoli, Italy), after decades of chemical contaminations and coastal transformation, to build a baseline for the next remediation and restoration programs. Historical occurrence of macroalgae and seagrasses before, during and after the industrial period was assessed; in particular, we focused the attention mainly on habitat-forming species, due to the vital function played in the trophic net. We observed no differences in the macroalgal diversity between the SIN district and the other parts of the Gulf of Pozzuoli, except for the Gulf of Pozzuoli during the industrial period, where the biodiversity showed a decreasing trend. However, a substantial regression of the largest macrophytes (Fucales) on rocky coasts and of marine monocots on sandy bottoms, all over the area, has been recorded. A loss of about 70% has concerned seagrass cover, mainly Posidonia oceanica, in the contaminated area of the SIN: at present, this engineering species is missing on the bottom, facing the industrialised area. The human-made coastline transformation, the lack of natural substrates and the spatial remoteness among donor populations seem to be the leading causes of the significant decrease, over time, of marine forests in this study area. These factors should be taken into account to establish conservation priorities and for plant restoration.

Long-term response of Dictyota dichotoma var. intricata (C. Agardh) Greville (Phaeophyceae) to ocean acidification: Insights from high pCO2 vents

The ocean acidification may severely affect macroalgal communities of the shallowest coastal habitats where they play relevant structural and functional roles. In this paper were investigated the physiological traits of two populations of Dictyota dichotoma var. intricata, living at two different pH for several generations to assess the reasons of the algae reduced abundance at current (8.1) compared to low pH (6.7). Besides, through transplant experiments, the two populations were analysed for the stress response and reversibility of physiological performance at different pH. The long-term acclimation to high pCO2/low pH favours an ecotype characterised by low energetic costs, higher photochemical efficiency and more resistance to the oxidative stress, compared to individuals living at current pH. These traits promoted the growth and reproduction of the community living at pH 6.7, favouring a lower macroalgal diversity, but a higher ecological success under ocean acidification. The similar behaviour observed between Dictyota living at pH 6.7 and transplanted thalli from pH 6.7 to 8.1, suggested a high tolerance to pH changes in the short-term. On the contrary, adaptive responses may have favoured molecular adjustments on the long-term, as showed by the significant differences between the wild populations at pH 8.1 and 6.7. The overall data indicate that both plasticity and adaptive mechanisms may be the reasons for the success of the brown seaweeds under future high pCO2/low pH. The plasticity due to photochemistry adjustments is likely involved in the early response to environmental changes. Conversely, modifications in the photosynthetic biochemical machinery suggest that more complex adaptive mechanisms occurred in the current population of Dictyota living at pH 6.7. Further studies on population genetics will reveal if any differentiation is taking place at the population level or a local adaptation has already occurred in Dictyota and other brown algae under chronic low pH.

Macroalgas de la laguna "El Carmen", Tabasco, México

Antecedentes y Objetivos: Debido a la escasez de conocimiento sobre macroalgas en lagunas costeras de Tabasco, en este trabajo se determina la diversidad ficoflorística de macroalgas asociadas a la laguna El Carmen, municipio de Cárdenas, y se contribuye al conocimiento biológico y ecológico en el estado de Tabasco. Métodos: Se realizaron tres muestreos en un ciclo anual de 2015 a 2016 durante la época de lluvias, la de nortes y la de secas. Los organismos se recolectaron manualmente, se fijaron con agua marina y formol al 4%, se identificaron y se depositaron en los herbarios FCME (UNAM) y UJAT. Resultados clave: Se reportan 21 especies de macroalgas marinas, tres de las cuales son nuevos registros para el estado de Tabasco. La división Rhodophyta con las familias Gracilariaceae y Rhodomelaceae tiene la mayor riqueza de especies; Gracilaria blodgetti es la más abundante. La temporada de nortes obtuvo la mayor riqueza y abundancia. Conclusiones: Se incrementó a 125 el número de registros de Rhodophyta y 28 de Ochrophyta para Tabasco. Se sugiere ampliar el número de muestreos sistemáticos en un ciclo anual con la finalidad de tener una mejor representación de la diversidad y la estacionalidad de las macroalgas en la laguna El Carmen.

Keanekaragaman dan Potensi Pemanfaatan Makroalga di Pesisir Pulau Tunda

Macroalgae is one of the marine biological resources that has a potential to be utilized further by humans. This research aims to study macroalgae diversity and utilization potency by humans in the coastal area of Tunda Island. The study was conducted at 4 stations using the belt transect method. Results of this study indicated that there were 15 species of macroalgae found that came from 3 macroalgae classes, they were chlorophyceae, phaeophyceae, and rhodophycea. Macroalgae species that are often found are Padina minor, Halimeda macroloba, and Gracilaria salicornia. The highest macroalgae diversity was found at station 3 with a value of 2.44. Based on the type of macroalgae found in the field there are several macroalgae species that can be utilized, and the lack of information causes the low macroalgae utilization by the local community. Keywords: Biodiversity, Gracilaria salicornia, Halimeda macroloba, macroalgae, Padina minor

Macroalgal diversity for sustainable biotechnological development in French tropical overseas territories

AbstractThis review focuses on the diversity of French tropical overseas macroalgae and their biotechnological applications. After listing the specific diversity, i.e. 641 species in French Antilles in the Atlantic Ocean, 560 species in the Indian Ocean, and 1015 species in the South Pacific Ocean, we present the potential of their metabolites and their main uses. Among the great diversity of metabolites, we focus on carbohydrates, proteins, lipids, pigments and secondary metabolites, in particular terpenes and phenolic compounds. The main applications of reef macroalgae are described in human and animal consumptions, phycocolloids extraction, production of active ingredients for health, cosmetics, agriculture, and bioremediation. For each application, we list what has been done, or will be done in French tropical overseas territories and point out the challenges faced when using this chemo-diversity, and problems linked to their exploitation. Finally, we discuss challenges to develop seaweed farming, their uses in carbon sequestration and resilience to global change, their uses for alternative proteins together with the production of bioenergy and biomaterials. As a conclusion, we encourage the research on the chemo-diversity of French reef macroalgae for industrial applications as these organisms represent a reservoir of active ingredients that is still insufficiently explored.

Macroalgal vegetation on a north European artificial reef (Loch Linnhe, Scotland): biodiversity, community types and role of abiotic factors

Very little is known about the marine macroalgae of artificial reefs—especially in the North Atlantic—despite the growing number and extent of man-made structures in the sea, and even though seaweed communities have paramount importance as primary producers, but also as feeding, reproductive and nursery grounds in coastal ecosystems. This paper explores the macroalgal diversity of a large system of artificial reefs in Loch Linnhe, on the west coast of Scotland, in a quantitative and qualitative study based on diving surveys and correlates the observations with the prevalent abiotic factors. The study was conducted in order to test the hypothesis that artificial reefs can enhance seaweed habitats—in particular, for kelps—and that there is a clear correlation with substrate type. While the reef is home to a large range of biota and abundance of early-successional species of turf and bushy macroalgae, totalling 56 taxa and with Delesseria sanguinea as the dominant species, canopy-forming perennial kelp species are conspicuously relatively rare. Macroalgal vegetation is explored in correlation with reef geometry/geography and depth. Statistical analysis shows benthic communities were strongly affected by substrate type, with turf algae and invertebrates dominating the artificial reefs, while bushy algae dominate the natural ones. Common macroinvertebrates associated with the phytobenthic communities are assessed qualitatively.

Lifestyle of the Octoradiate Eoandromeda in the Ediacaran

The octoradiate Eoandromeda Tang et al. from the Ediacaran of South China and South Australia is poorly understood and there are different interpretations of its morphology and paleoecology. The carbonaceous compression known as Eoandromeda, which is collected in black shales of the upper Doushantuo Formation in northeastern Guizhou, South China, shows various patterns and complex structures. Eoandromeda is interpreted as an umbrella-shaped metazoan, with a dome-shaped polar structure on the top of its body, eight dextrally spiraling arms and tapering skirts. The spiral arms are differentiated into a main segment consisting of rigid and thick masses and a distal segment consisting of flexible and thin masses. Thus, we consider that the spiral arms may have consisted of gelatinous masses and primarily grew in their distal segments (approximately the tapering skirts). The numerous feather-like structures on the platy spiral arms are regularly arranged into two longitudinal rows. We believe that Eoandromeda lived in a primitive “Seabed Grassland” with an abundance and diversity of macroalgae and was capable of swimming in the water column by flapping its feather-like structures. Based on measurements of the maximum diameter of the disk-shaped compression and the maximum width of the spiral arms, Eoandromeda can be divided into a juvenile stage (< 10 mm diameter) that has not been found, an adult stage (10–30 mm diameter) with a high growth rate in the width of the spiral arms, and a senescent stage (> 30 mm diameter) with a slow growth rate in the width of the spiral arms. Fully grown Eoandromeda, with thick and rigid spiral arms, may have mostly stayed on the sediment surface, temporarily swimming to seek new habitat or prey. The juveniles, better swimmers, may have had a soft body with soft and thin arms, unlikely to be preserved, and may have been easily transported by water currents.

Biodiversity of macroalgae in Pari Island

Macroalgae is one of the marine biological resources that have the potential to be utilized further by humans. This research aims to study macroalgae diversity in Pari Island. The study was conducted at two stations using the line transect method at the reef flat area. The results of this study indicate that there are 3 class macroalgae found in Pari Island. 17 species of macroalgae found in the south of Pari Island and 10 species found at the North of Pari Island. Macroalgae species with high abundance are Padina minor and Halimeda opuntia. The highest macroalgae diversity was found at south Pari Island with a diversity value index 2.02.

Distribution and diversity of Macroalgae in the Andaman region, India

Distribution and diversity of Macroalgae in the Andaman region, India

Study of the macroalgae and application of ecological evaluation index (EEI-c) in the coastal waters of Algeria

The diversity of macroalgae and evaluation of the Algerian coastal waters using EEI-c index were studied. Macroalgae were sampled at seven stations in summer 2019. Coverage data for the macroalgae at each site were analysed at species level. Eleven species have been identified and the results showed the prevalence of Cystoseira compressa and Ulva sp .. The least abundant species were Cladophora sp. and Corallina elongata . Classification of sites based on the cluster analysis shewed an agreement with the water degradation information. Based on the results, the EEI-c values were quite homogeneous over all the studied sites, and generally correspond to undisturbed states except for one site.

Population Structure of the Red Macroalga Botryocladia occidentalis (Børgesen) Kylin (Rhodymeniaceae, Rhodymeniales) in the Gulf of Mexico Before the Deepwater Horizon Oil Spill

Studies on the population structure of common widespread macroalgae in the Gulf of Mexico (GoMx) are scarce, and this knowledge gap limits our understanding on how disturbances affect the genetic diversity of macroalgae in this basin. The latter is due to the lack of a baseline that can be compared with allele frequency surveys conducted after a major disturbance such as the 2010 Deepwater Horizon oil spill (DWH), which leaked 780,000 m3 of crude oil in the vicinity of highly diverse macroalgal communities. Fortunately, quantitative assessments of the population structure pre-DWH can be accomplished for several macroalgae with dried specimens collected from research cruises conducted before 2010 in the offshore GoMx. Based on three markers (cytochrome c oxidase subunit I, COX II-III intergenic spacer, and the RuBisCO large subunit), this study reconstructed the allele frequencies pre-DWH for a GoMx-widespread macroalga, Botryocladia occidentalis, and revealed the existence of distinct populations in each of three distant regions of the GoMx: Florida Middle Grounds (FL), Campeche Banks (CB), and offshore Louisiana (LA). Population structure was assessed with exact tests of population differentiation and Analyses of Molecular Variance. FL harbored the most differentiated and genetically diverse population due to the presence and abundance of unique haplotypes. Interestingly, FL haplotypes were not closely phylogenetically related to each other and included the most divergent lineages of the entire GoMx; this phylogeographic pattern suggests a strong influence of migrants from the Caribbean on the FL population. Additionally, likelihood ratio tests with a small sample collected post-DWH indicated that the LA population underwent strong changes, showing statistically significant differences before (LA) vs. after (L2) the disaster. Whereas the LA population had affinity to CB, L2 showed a FL haplotype that, before the disaster, had never been reported in LA or CB. Such changes may not be permanent but rather a temporary response to disturbance; also, they may not necessarily be caused by the spilled oil but by other factors associated with the DWH.