Marine Benthic Ecosystems Research Articles

Larval dispersal and physical connectivity of Pheronema carpenteri populations in the Azores

The study of larval dispersal and connectivity between deep-sea populations is essential for the effective conservation and management of deep-sea environments and the design and implementation of Marine Protected Areas. Dense sponge aggregations, known as “sponge grounds”, are a key component of marine benthic ecosystems, by increasing the structural complexity of the sea floor and providing structure and habitat for many other species. These aggregations are characteristic of the Azores deep-sea environment. These sessile organisms rely primarily on larval dispersal for their reproduction. Connectivity between specific Pheronema carpenteri sponge aggregations in the Azores was studied using a 3-D biophysical dispersal model. Different biological trait scenarios were analyzed, considering spawning seasonality and pelagic larval duration. Model results indicate that regional circulation patterns drive larval dispersion, shaping population connectivity of P. carpenteri sponge aggregations in the Azores, particularly among aggregations in the Central Group of Azorean islands. Some areas present high retention rates, receiving larvae from several sponge aggregations while also being important larval source aggregations. In contrast, aggregations from the Eastern Group may be isolated from the others. Larval dispersal and connectivity patterns were analyzed concerning the current configuration of Marine Protected Areas (MPAs) in the Azores. The results underscored the importance of maintaining protection efforts in existing MPAs and identified stepping-stone locations and specific sites where additional measures could enhance species connectivity in the Azores.

Contrasting metal bioaccumulation in marine benthic invertebrate groups in polluted harbor sediments

This study examined the sediment metal fractions and availability to infer bioaccumulation in marine harbor benthic organisms. Total metals were analyzed using atomic absorption spectrometry and inductively coupled plasma-optical emission spectrometry for chemical fractions and organisms. The results showed similar metal concentrations and distribution driven by rivers and harbor pollution. We found significant differences in metal accumulation in marine benthic groups, highest in scavenger species. Their metal concentrations in decreasing order were 1.97–4568, 0.10–1260, 1.64–159, and 0.105–112 μg g−1 dw for hermit crabs, forams, bivalves, and polychaetes. Moreover, certain organisms, such as tusk shells, sea pens, bivalves, forams, and isopods, may exhibit selective metal accumulation. Biota-sediment accumulation factors (>1) were highest for essential metals like Cu, Zn, and Mn, while toxic metals like As, Cr, Co, and Ni increased. This concurrent assessment provides more comprehensive data for metal bioaccumulation in marine benthic ecosystems.

The Roles of Alpha, Beta, and Functional Diversity Indices in the Ecological Connectivity between Two Sub-Antarctic Macrobenthic Assemblages

The study of ecological connectivity is a global priority due to the important role it plays in the conservation of diversity. However, few studies in this context have focused on marine benthic ecosystems. To address this issue, the present work determines the ecological connectivity between two sub-Antarctic macrobenthic assemblages through assessment of the α-, β-, and functional diversity indices. Samples were collected using a van Veen grab at stations located in Bahia Inútil and Seno Almirantazgo. The ecological analysis was based on a total of 113 invertebrate taxa. The mean abundance values were lower in Bahia Inútil (888.9 ± 26.8 ind m−2) than in Seno Almirantazgo (1358.6 ± 43.4 ind m−2). While the mean α-diversity values showed significant differences between assemblages, β- and functional diversity indices presented no significant differences. These results indicate that, despite the distance (56 km) separating the two basins from each other, there is a high degree of connectivity at the functional level between the assemblages due to the high number of shared species and their functional traits. The species most responsible for this observation were the polychaetes Capitela capitata and Aricidia (Acmira) finitima, as well as the bivalves Nucula pisum and Yoldiella sp. 1. In terms of functional biodiversity, species characterized as omnivorous and with lecithotrophic larval development were mostly responsible for connectivity between assemblages. These results suggest the importance of including β- and functional diversity indices as criteria in the future planning of marine protected areas for the maintenance of marine ecosystem integrity.

Effect of temperature and body size on anterior and posterior regeneration in Hermodice carunculata (Polychaeta, Amphinomidae)

In recent years, population outbreaks of the annelid Hermodice carunculata (Polychaeta, Amphinomidae) are recurrently detected along the coastal zone of the Salento peninsula (Southern Italy), with impacts on marine benthic ecosystems. Annelida are renowned for their remarkable regeneration potential, enabling them to reform lost body parts. A handful of studies have reported posterior regeneration of H. carunculata, but anterior regeneration has not been fully explored. In this study, we investigated the capacity of H. carunculata collected in shallow coastal areas (Ionian Sea, 40°08’26.9” N 17°58’44.1” E) to regenerate anterior body parts under different temperature conditions (22 and 14 °C) and considering two different body sizes (∼ 4 g and 25 g). In addition, histological analysis and lipid analyses were carried out to detect changes in the reproductive cycle and lipid storage during ongoing regeneration. The results suggest that small and large-sized specimens of H. carunculata can regenerate efficiently anterior body parts in 12–20 weeks post amputation when kept at 22 °C. Small-sized worms kept at 14 °C regenerated slower but died in 24 weeks post amputation before regenerating a mouth, while large-sized worms kept at 14 °C were affected by a 100% mortality during blastema formation. In addition, lipid extraction analyses show that H. carunculata can regenerate during extended periods of starvation by de novo synthesizing lipid reserves and regeneration in H. carunculata does not negatively impact the reproductive cycle, as gametogenesis occurs also during the regenerative processes.

Evidence of size-dependent toxicity of polystyrene nano- and microplastics in sea cucumber Apostichopus japonicus (Selenka, 1867) during the intestinal regeneration

Microplastics are ubiquitous pollutants in the global marine environment. However, few studies have adequately explored the different toxic mechanisms of microplastics (MPs) and nanoplastics (NPs) in aquatic organisms. The sea cucumber, Apostichopus japonicus, is a key organism in the marine benthic ecosystem due to its crucial roles in biogeochemical cycles and food web. This study investigated the bioaccumulation and adverse effects of polystyrene micro- and nanoplastics (PS-M/NPs) of different sizes (20 μm, 1 μm and 80 nm) in the regenerated intestine of A. japonicus using multi-omics analysis. The results showed that after 30-day exposure at the concentration of 0.1 mg L−1, PS-MPs and PS-NPs accumulated to 155.41–175.04 μg g−1 and 337.95 μg g−1, respectively. This excessive accumulation led to increased levels of antioxidases (SOD, CAT, GPx and T-AOC) and reduced activities of immune enzymes (AKP, ACP and T-NOS), indicating oxidative damage and compromised immunity in the regenerated intestine. PS-NPs had more profound negative impacts on cell proliferation and differentiation compared to PS-MPs. Transcriptomic analysis revealed that PS-NPs primarily affected pathways related to cellular components, e.g., ribosome, and oxidative phosphorylation. In comparison, PS-MPs had greater influences on actin-related organization and organic compound metabolism. In the PS-M/NPs-treated groups, differentially expressed metabolites were mainly amino acids, fatty acids, glycerol phospholipid, and purine nucleosides. Additionally, microbial community reconstruction in the regenerated intestine was severely disrupted by the presence of PS-M/NPs. In the PS-NPs group, Burkholderiaceae abundance significantly increased while Rhodobacteraceae abundance decreased. Correlation analyses demonstrated that intestinal regeneration of A. japonicus was closely linked to its enteric microorganisms. These microbiota-host interactions were notably affected by different PS-M/NPs, with PS-NPs exposure causing the most remarkable disruption of mutual symbiosis. The multi-omic approaches used here provide novel insights into the size-dependent toxicity of PS-M/NPs and highlight their detrimental effects on invertebrates in M/NPs-polluted marine benthic ecosystems.

In Vitro Toxicity and Modeling Reveal Nanoplastic Effects on Marine Bivalves.

Nanoplastics (NPs) represent a growing concern for global environmental health, particularly in marine ecosystems where they predominantly accumulate. The impact of NPs on marine benthic organisms, such as bivalves, raises critical questions regarding ecological integrity and food safety. Traditional methods for assessing NP toxicity are often limited by their time-intensive nature and ethical considerations. Herein, we explore the toxicological effects of NPs on the marine bivalve Ruditapes philippinarum, employing a combination of in vitro cellular assays and advanced modeling techniques. Results indicate a range of adverse effects at the organismal level, including growth inhibition (69.5-108%), oxidative stress, lipid peroxidation, and DNA damage in bivalves, following exposure to NPs at concentrations in the range of 1.6 × 109-1.6 × 1011 particles/mL (p/mL). Interestingly, the growth inhibition predicted by models (54.7-104%), based on in vitro cellular proliferation assays, shows strong agreement with the in vivo outcomes of NP exposure. Furthermore, we establish a clear correlation between cytotoxicity observed in vitro and the toxicological responses at the organismal level. Taken together, this work suggests that the integration of computational modeling with in vitro toxicity assays can predict the detrimental effects of NPs on bivalves, offering insightful references for assessing the environmental risk assessment of NPs in marine benthic ecosystems.

Are physiological and ecosystem-level tipping points caused by ocean acidification? A critical evaluation

Abstract. Ocean acidification (OA) is predicted to cause profound shifts in many marine ecosystems by impairing the ability of calcareous taxa to calcify and grow and by influencing the physiology of many others. In both calcifying and non-calcifying taxa, ocean acidification could further impair the ability of marine life to regulate internal pH and thus metabolic function and/or behaviour. Identifying tipping points at which these effects will occur for different taxa due to the direct impacts of ocean acidification on organism physiology is difficult because they have not adequately been determined for most taxa nor for ecosystems at higher levels. This is due to the presence of both resistant and sensitive species within most taxa. However, calcifying taxa such as coralline algae, corals, molluscs, and sea urchins appear to be most sensitive to ocean acidification. Conversely, non-calcareous seaweeds, seagrasses, diatoms, cephalopods, and fish tend to be more resistant or even benefit from the direct effects of ocean acidification, though the effects of ocean acidification are more subtle for these taxa. While physiological tipping points of the effects of ocean acidification either do not exist or are not well defined, their direct effects on organism physiology will have flow-on indirect effects. These indirect effects will cause ecological tipping points in the future through changes in competition, herbivory, and predation. Evidence for indirect effects and ecological change is mostly taken from benthic ecosystems in warm temperate–tropical locations in situ that have elevated CO2. Species abundances at these locations indicate a shift away from calcifying taxa and towards non-calcareous taxa at high-CO2 concentrations. For example, lower abundance of corals and coralline algae and higher covers of non-calcareous macroalgae, often turfing species, are often found at elevated CO2. However, there are some locations where only minor changes or no detectable changes occur. Where ecological tipping points do occur, it is usually at locations with naturally elevated mean pCO2 concentrations of 500 µatm or more, which also corresponds to just under that concentration where the direct physiological impacts of ocean acidification are detectable in the most sensitive taxa in laboratory research (coralline algae and corals). Collectively, the available data support the concern that ocean acidification will most likely cause ecological change in the near future in most benthic marine ecosystems, with tipping points in some ecosystems as low as 500 µatm pCO2. However, further research is required to more adequately quantify and model the extent of these impacts in order to accurately project future marine ecosystem tipping points under ocean acidification.

Behavioral and physiological responses of nocturnal marine shellfish to predation pressure

Predator-prey interactions are critical in ecological communities. As the wild resources of Pacific abalone are on the verge of exhaustion, efforts to reveal the effects of predation by hostile organisms on the efficiency of its bottom sowing and proliferation are crucial for the success of resource restoration. In this study, abalone and its predator, starfish Asterias amurensis, were placed in a customized monitoring unit. Through continuous infrared video monitoring, predation pressure was found to cause a significant decrease in the distance moved, duration of movement, cumulative feeding duration and orexin levels in hemolymph (P < 0.01). It also caused a significant increase in the average velocity of movement, group cohesion, coordination and cholecystokinin levels in hemolymph (P < 0.01). Surprisingly, when a shelter was set up in the environment, the cumulative feeding duration of abalone was significantly extended in the presence of the predator (P < 0.001), whereas when the predator was removed, the distance moved, duration of movement, and cumulative feeding duration of abalone were found to significantly increase during continuous 24 h monitoring (P < 0.01). These results first identified the anti-predation strategy by nocturnal marine organisms when exposed to predation risk, and supported the pivotal role of shelter in helping abalone make a trade-off between predation pressure and survival needs, which not only provides a new insight to optimizing the strategy for prevention and control of marine ecological disasters and strengthening the protection of marine endangered species, but also results in a productive attempt to restore the marine benthic ecosystem.

Triterpene Glycosides from the Viscera of Sea Cucumber Apostichopus japonicus with Embryotoxicity.

Sea cucumbers release chemical repellents from their guts when they are in danger from predators or a hostile environment. To investigate the chemical structure of the repellent, we collected and chemically analyzed the viscera of stressed sea cucumbers (Apostichopus japonicus) in the Yellow Sea of China. Two undescribed triterpene glycosides (1 and 2), together with a known cladoloside A (3), were identified and elucidated as 3β-O-{2-O-[β-d-quinovopyranosyl]-4-O-[3-O-methyl-β-d-glucopyranosyl-(1→3)-β-d-glucopyranosyl]-β-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (1), 3β-O-{2-O-[β-d-glucopyranosyl]-4-O-[3-O-methyl-β-d-glucopyranosyl-(1→3)-β-d-glucopyranosyl]-β-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (2), 3β-O-{2-O-[3-O-methyl-β-d-glucopyranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-β-d-quinovopyranosyl]-β-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (3) by spectroscopic analysis, including HR-ESI-MS and NMR spectra. Compounds 1, 2, and 3 display embryonic toxicity, as indicated by their 96-hour post-fertilization lethal concentration (96 hpf-LC50) values of 0.289, 0.536, and 0.091 μM, respectively. Our study discovered a class of triterpene glycoside compounds consisting of an oligosaccharide with four sugar units and a holostane aglycone. These compounds possess embryotoxicity and may serve as chemical defense molecules in marine benthic ecosystems.

A marine heatwave changes the stabilizing effects of biodiversity in kelp forests.

Biodiversity can stabilize ecological communities through biological insurance, but climate and other environmental changes may disrupt this process via simultaneous ecosystem destabilization and biodiversity loss. While changes to diversity-stability relationships (DSRs) and the underlying mechanisms have been extensively explored in terrestrial plant communities, this topic remains largely unexplored in benthic marine ecosystems that comprise diverse assemblages of producers and consumers. By analyzing two decades of kelp forest biodiversity survey data, we discovered changes in diversity, stability, and their relationships at multiple scales (biological organizational levels, spatial scales, and functional groups) that were linked with the most severe marine heatwave ever documented in the North Pacific Ocean. Moreover, changes in the strength of DSRs during/after the heatwave were more apparent among functional groups than both biological organizational levels (population vs. ecosystem levels) and spatial scales (local vs. broad scales). Specifically, the strength of DSRs decreased for fishes, increased for mobile invertebrates and understory algae, and were unchanged for sessile invertebrates during/after the heatwave. Our findings suggest that biodiversity plays a key role in stabilizing marine ecosystems, but the resilience of DSRs to adverse climate impacts primarily depends on the functional identities of ecological communities.

Ecological monitoring of the Russian continental shelf of Arctic seas: criterion selection, assessment, and prospects

The article provides an analytical review of long-term studies assessing the ecological state of Arctic marine ecosystems. The focus is on integral estimation methods. The issues associated with the application of biological methods for assessing the ecological state of the Russian continental shelf of Arctic seas are considered. The author briefly reviews existing methods for biotesting the marine environment and provides examples of the use of biotest systems. On the example of model benthic communities, an ecological assessment of marine benthic ecosystems is presented.

Impact of hydrological changes and vertical motions on Pleistocene marine environments of the eastern coast of the island of Rhodes (Greece)

The island of Rhodes in the eastern Mediterranean Sea is situated in an area affected by an ongoing plate convergence, and its Pleistocene marine environments were influenced by recurring hypoxia and changes in organic matter fluxes. This makes the island an important site to study the influence of orbital-driven climate changes and tectonic-induced vertical motions on the marine benthic ecosystems in near-coastal areas at local and regional scales. We investigated the Early and Late Pleistocene sediment sections at Agathi Beach and Lardos, located on the middle-eastern coast of the island. Our results show variations in oxygen and food levels at the sea floor, including transient phases of enhanced fresh-water and nutrient input to near-coastal environments. These phases occurred at times of Northern Hemisphere summer insolation maxima, simultaneously to the formation of sapropels in the deep-sea basins of the eastern Mediterranean Sea. The application of a benthic foraminiferal transfer function revealed that both sections were influenced by tectonic-driven long-term and short-term vertical motions with higher rates than expected on the island of Rhodes. While Agathi Beach underwent two short-term cycles of uplift and subsidence, Lardos indicates at least three cycles with average rates of vertical motion as high as 8.6 mm/a.

Increased habitat segregation at the dawn of the Phanerozoic revealed by correspondence analysis of bioturbation

The Agronomic Revolution of the early Cambrian refers to the most significant re-structuration of the benthic marine ecosystem in life history. Using a global compilation of trace-fossil records across the Ediacaran-Cambrian transition, this paper investigates the relationship between the benthos and depositional environments prior to, during, and after the Agronomic Revolution to shed light on habitat segregation via correspondence analysis. The results of this analysis characterize Ediacaran mobile benthic bilaterians as facies-crossing and opportunistic, with low levels of habitat specialization. In contrast, the Terreneuvian and Cambrian Series 2 reveal progressive habitat segregation, parallel to matground environmental restriction. This event was conducive to the establishment of distinct endobenthic communities along the marine depositional profile, showing that the increase in styles of animal-substrate interactions was expressed by both alpha and beta ichnodiversity. Habitat segregation at the dawn of the Phanerozoic may illustrate an early extension of the trophic group amensalism at community scale.

Ecosystem function modified by an invasive species: Density and distance dependent changes in sediment characteristics, fluxes, and benthic communities

Coastal marine benthic ecosystems are considered hotspots for biodiversity and productivity. However, the introduction of bio-engineering non-indigenous species can alter the delivery of key functions and services provided by these systems. Here, we investigated the influence of Sabella spallanzanii, a large structure-forming invasive polychaete, on a marine soft-sediment system in New Zealand, examining effects on sediment characteristics (organic matter and chlorophyll a content), solute fluxes, and benthic communities near and far from low-, medium-, and high-density clumps of Sabella. Fluxes of dissolved oxygen and inorganic nitrogen near (<10 cm) Sabella clusters were significantly lower to those 1 m away, and fluxes differed between low-, medium-, and high-density clumps. Larger densities of Sabella and clumps with greater overall biomass were associated with increased sediment oxygen consumption, particularly in areas 1 m distant from the Sabella clumps. Similarly, ammonium production (efflux from the sediment) increased with increasing Sabella biomass at the 1 m ‘distal’ sites (from 0 μ to 40 μmol/m2/h), but NOx efflux decreased (from 5 to 0 μmol/m2/h) with distance. The flux results were consistent with findings of higher organic matter content and finer grain size sediment in ‘distal’ plots to Sabella clusters. We also showed how benthic diversity and abundance increased with increasing Sabella clump biomass. Our investigation suggests that the building of biogenic structures and the filter feeding activity by Sabella may alter near-bed flows and concentrations of organic rich biodeposits in surrounding sediments, with ramifications for organic matter distribution and nutrient recycling rates. The continuous expansion and colonisation of Sabella could reshape local benthic communities and increase oxygen consumption rates in affected marine sediments.

Morphological and molecular study of Syllinae (Annelida, Syllidae) from Bermuda, with the description of five new species.

Although polychaetes from the Bermuda Archipelago have been studied since the beginning of the twentieth century, syllids have been particularly neglected in this area, which is surprising considering this family is usually a dominant group in marine benthic ecosystems. To fill this knowledge gap, we have carried out an extensive analysis of Bermudan Syllidae, combining morphological and molecular data including four nuclear and mitochondrial markers (cytochrome c oxidase subunit I, 18S rRNA, 16S rRNA and 28S rRNA). We have identified and established the phylogenetic position of five new species, Haplosyllis anitae n. sp., Haplosyllis guillei n. sp., Haplosyllis larsi n. sp., Haplosyllis vassiae n. sp. and Syllis laiae n. sp., together with Haplosyllis cf. cephalata. Overall, our results extend the knowledge on the diversity of Syllidae in Bermuda, increasing the number of species present in the area to 25. Our results also recover Opisthosyllis and Syllis as non-monophyletic genera, for which traditional diagnostic morphological features do not accurately reflect their evolutionary histories, and thus we propose that these groups should be reorganized based on molecular characters.

Mapping fine-scale demersal trawl effort for application in ecosystem assessment and spatial planning

Fine-scale maps of fishing activity are valuable information layers for fisheries management, assessments of biodiversity impacts and marine spatial planning. Our aim was to develop an accurate map of demersal trawling intensity in South Africa and to demonstrate its utility at a national scale. We calculated a swept area ratio, representing demersal trawling effort for the entire study period (2005‒2018) and annually. We then plotted spatial and temporal patterns of trawling activity, identified core fishing areas, and examined spatial overlap between trawling, South Africa’s marine ecosystem types and the national network of marine protected areas. A high proportion of trawling effort (90%) was concentrated in 43% of the area exposed to trawling, with the remaining 10% spread across 57% of the fished areas. The fishery overlaps with 33 of 150 benthic and bentho-pelagic marine ecosystem types. Of those, 11 have more than 50% of their extent, and five have more than 80%, within the trawl ring-fence. Our analyses support a systematic prioritisation of ecosystem types for further management and protection. The new South African trawling-intensity map contributes an improved pressure layer for ecosystem assessments, can help identify priority fishing areas and has application in conservation, marine spatial planning and fisheries management.

Biotic recovery after the Late Ordovician Mass Extinction Event: insights from ichnofossils of the middle–upper Yangtze Block, South China

ABSTRACT The timing and pattern of biotic recovery after the Late Ordovician Mass Extinction (LOME) are highly controversial. Here, we conducted a systematic investigation on ichnofossils from the lower Silurian succession of the northwestern Hunan province, middle-upper Yangtze Block, South China. Biotic recovery of marine benthic ecosystems after the LOME was analysed and discussed for the first time using multiple ichnofossil proxies. The vertical distribution and evolutional trends of trace fossil assemblages suggest that biotic recovery was significantly delayed by the widespread anoxia during the latest Hirnantian to middle Aeronian. The recovery displays a stepwise pattern and reached a relatively high stage during the late Aeronian, although a full recovery was generally not achieved during this interval as proposed elsewhere before. There is a sharp decrease in all trace fossil proxies across the Aeronian-Telychian boundary, indicating a resetting of biotic recovery back to initial stages, most likely linked to a re-onset of anoxia in shallow marine settings during the late Aeronian Event. Subsequent recovery generally followed the patterns of late Aeronian, but was hampered by a low nutrient supply during early Telychian. By the beginning of middle Telychian, a full recovery was achieved, ca. 8.8 Ma after the second pulse of the LOME.

De novo transcriptome assembly of Iphiculus spongiosus Adams & White, 1849 (Decapoda; Brachyura; Leucosioidea) using full-length isoform sequencing

Brachyura play a key role in linking food energy transfer in marine benthic ecosystems. Hence, the health and sustainability of benthic ecosystems come from the maintenance of crab diversity, and systematic studies should be performed. Recently, although mitochondrial genomes have been widely used in brachyuran phylogeny, the systematic reconstruction of leucosiid crabs has mainly depended on museum specimens due to the lack of live specimens and reference databases. Here, therefore, the selected ribonucleic acid (RNA) was isolated from Iphiculus spongiosus for long-read, single molecule sequencing based on the PacBio full-length isoform sequencing (ISO-seq) platform. A total of 173,863 high-quality consensus isoforms were obtained with a total sequencing length of 210,170,210 bp. Performing functional annotation by including seven general databases revealed a total of 73,809 transcripts (based on the identified coding region sequences), of which the total length was 56,483,844 bp. These results represent the first RNA sequencing data of the leucosiid group. They can contribute to the de novo transcriptome assembly of a reference database and could aid the development of genetic probes to aid target sequence capture in future taxonomic studies.

Detection of global change with meiofauna and its benthic environment in a shelf sea cold water mass ecosystem

The marine benthic ecosystems can be affected by global environmental change. The northern Yellow Sea cold water mass (NYSCWM) is locally generated without external intrusion, and relatively independent and sensitive to global change. We utilized multiple scale temporal data collected during 12 cruises (2006–2014) to detect potential impact of global change on meiofauna and its benthic environment in the NYSCWM ecosystem. Time series of bottom water temperature and total organic carbon exhibited increasing trends, while those of meiofaunal abundance, biomass, sedimentary chlorophyll a and bottom water salinity exhibited decreasing trends. The temporal trends observed in our study were coincident with the global reduction of benthic standing stock in response to global change and anthropogenic disturbance. The strong seasonality of meiofauna, however, may mask its long-term pattern, and meiofauna with its sedimentary environment may serve as an integrated indicator of potential impact of global change on the shelf sea cold water mass ecosystem only if longer-term monitoring data can be accumulated and seasonal effect taken into account.

Systematic paleontology of macroalgal fossils from the Tonian Mackenzie Mountains Supergroup

AbstractProterozoic eukaryotic macroalgae are difficult to interpret because morphological details required for proper phylogenetic studies are rarely preserved. This is especially true of morphologically simple organisms consisting of tubes, ribbons, or spheres that are commonly found in a wide array of bacteria, plants, and even animals. Previous reports of exceptionally preserved Tonian (ca. 950−900 Ma) fossils from the Dolores Creek Formation of Northwestern Canada feature enough morphological evidence to support a green macroalgal affinity. However, the affinities of two additional forms identified on the basis of the size distribution of available specimens remain undetermined, while the presence of three unique algal forms supports other reports of increasing algal diversity in the early Neoproterozoic. Archaeochaeta guncho new genus new species is described as a green macroalga on the basis of its well-preserved morphology consisting of an unbranching, uniseriate thallus with uniform width throughout and possessing an elliptical to globose anchoring holdfast. A larger size class of ribbon-like forms is interpreted as Vendotaenia sp. A third size class is significantly smaller than Archaeochaeta n. gen. and Vendotaenia, but in the absence of clear morphological characters, it remains difficult to assign. As Archaeochaeta n. gen. and Vendotaenia represent photoautotrophic taxa, these findings support the hypothesis of increasing morphological complexity and phyletic diversification of macroalgae during the Tonian, leading to dramatic changes within benthic marine ecosystems before the evolution of animals.