Changes In Marine Environment Research Articles

Using stable isotopes as tracers of water masses and nutrient cycling processes in the Gulf of Maine

The dramatic marine environmental change seen today can be difficult to fully document and interpret without adequate, spatially and temporally comprehensive, baseline datasets of hydrographic properties. Here we present isotope data measured in water samples collected during a nine-day research cruise in October 2016 throughout the Gulf of Maine, a rapidly changing region of the world's oceans. A comparison of the oxygen isotopes of the water (δ18Owater) and salinity data reveal that water samples fall on a tight, linear mixing line between fresher shelf water and saltier slope waters, with the freshwater endmember originating from much higher latitudes (the Gulf of St. Lawrence and the Labrador Sea). Some subtle differences in freshwater endmembers are observed between the three different deep basins in the Gulf of Maine. These differences are likely reflecting differences in freshwater input and vertical mixing between the different basins. Additionally, these water samples have lower δ18Owater values for a given salinity value than previously published values of marine water mass endmembers. This offset may be related to systematic changesin water mass endmember values or year to year variability, as well as differences in the proportions of water masses entering the Gulf of Maine. Nitrogen and oxygen isotopes of dissolved nitrate (NO3−; δ15NNO3- and δ18ONO3-, respectively) measured in the water samples suggest a strong influence of phytoplankton assimilation near the surface in both isotopic systems. Combining these two datasets using Δ(15, 18) to look at the rates of fractionation between the two isotope systems reveals potential water column nitrification above 100 m in most places in the Gulf of Maine. This finding provides support for previous hypotheses of water column nitrification in the Gulf of Maine based on nutrient distribution and nitrogen box modeling. However, these calculations rely on the assumption that all nitrate is sourced from deeper waters. It is possible these results are instead caused by NO3− from different sources at the surface and therefore do not necessarily indicate the presence of nitrification.

Evolutionary responses of marine organisms to urbanized seascapes.

Many of the world's major cities are located in coastal zones, resulting in urban and industrial impacts on adjacent marine ecosystems. These pressures, which include pollutants, sewage, runoff and debris, temperature increases, hardened shorelines/structures, and light and acoustic pollution, have resulted in new evolutionary landscapes for coastal marine organisms. Marine environmental changes influenced by urbanization may create new selective regimes or may influence neutral evolution via impacts on gene flow or partitioning of genetic diversity across seascapes. While some urban selective pressures, such as hardened surfaces, are similar to those experienced by terrestrial species, others, such as oxidative stress, are specific to aquatic environments. Moreover, spatial and temporal scales of evolutionary responses may differ in the ocean due to the spatial extent of selective pressures and greater capacity for dispersal/gene flow. Here, we present a conceptual framework and synthesis of current research on evolutionary responses of marine organisms to urban pressures. We review urban impacts on genetic diversity and gene flow and examine evidence that marine species are adapting, or are predicted to adapt, to urbanization over rapid evolutionary time frames. Our findings indicate that in the majority of studies, urban stressors are correlated with reduced genetic diversity. Genetic structure is often increased in urbanized settings, but artificial structures can also act as stepping stones for some hard‐surface specialists, promoting range expansion. Most evidence for rapid adaptation to urban stressors comes from studies of heritable tolerance to pollutants in a relatively small number of species; however, the majority of marine ecotoxicology studies do not test directly for heritability. Finally, we highlight current gaps in our understanding of evolutionary processes in marine urban environments and present a framework for future research to address these gaps.

Evolution of Palaeoenvironment of the South Yellow Sea Since the Last Deglaciation

The sediments in core YS01 recovered from the South Yellow Sea mud deposit zone contain abundant benthic foraminifera, particularly shallow continental shelf species, but rare of planktonic foraminifera. The benthic foraminifera are dominated by stenohaline cold shallow-water species and euryhaline brackish-water species. In this paper, the palaeoenvironmental changes were discussed based on the grain-size compositions and benthic foraminiferal assemblages. Six different benthic foraminiferal assemblages were discriminated by species analysis from the foraminiferal fauna. According to AMS14C dating data in core YS01, we identified four main stages of marine environmental changes since the last deglaciation: a near-shore depositional stage (13.1–9.5 kyr B.P.), a transitional stage from near-shore deposition to shallow-sea deposition (9.5–5.6kyrB.P.), a high sea level stage with shallow-sea deposition (5.6–2.9kyrB.P.), and a stable shallow-sea depositional stage (2.9kyr B.P. to the present).

Temperature changes across the Paleocene-Eocene Thermal Maximum – a new high-resolution TEX86 temperature record from the Eastern North Sea Basin

The Paleocene-Eocene Thermal Maximum (PETM; ∼55.9 Ma) was a hyperthermal event associated with large carbon cycle perturbations, sustained global warming, and marine and terrestrial environmental changes. One possible trigger and/or source of the carbon release that initiated the PETM is the emplacement of the North Atlantic Igneous Province (NAIP). This study focuses on an expanded section of marine clays and diatomite on Fur Island in northern Denmark, where the entire PETM sequence has been identified by a negative ∼4.5‰ δ13CTOC excursion. This remarkably well-preserved section also contains >180 interbedded ash layers sourced from the NAIP, making it an ideal site for investigating the correlations between large-scale volcanism and environmental changes. This study provides a new and complete high-resolution TEX86-derived sea-surface temperature (SST) reconstruction over the entire PETM and the post-PETM section (up to about 54.6 Ma). The palaeothermometry record indicates an apparent short-lived cooling episode in the late Paleocene, followed by a pronounced temperature response to the PETM carbon cycle perturbations with a ∼10°C SST increase during the PETM onset (up to ∼33°C). Extreme SSTs fall shortly after the PETM onset, and continue to decrease during the PETM body and recovery, down to anomalously cool SSTs post-PETM (∼11–23°C). Both phases of potential cooling coincide with proxies of active NAIP volcanism, suggesting a causal connection, although several overprinting non-thermal factors complicate interpretations of the TEX86 values. Indices of effusive and explosive NAIP volcanism are largely absent from the Danish stratigraphy during the PETM body, though a re-emergence toward the end of the PETM suggest NAIP volcanism might have played a role in the PETM termination in the North Sea. This new SST record completes the previous fragmented view of climate changes at this globally important PETM site, and indicates large temperature variations in the North Sea during the earliest Eocene that are possibly linked to NAIP volcanism.

High predictability of direct competition between marine diatoms under different temperatures and nutrient states.

The distribution of marine phytoplankton will shift alongside changes in marine environments, leading to altered species frequencies and community composition. An understanding of the response of mixed populations to abiotic changes is required to adequately predict how environmental change may affect the future composition of phytoplankton communities. This study investigated the growth and competitive ability of two marine diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana, along a temperature gradient (9–35°C) spanning the thermal niches of both species under both high‐nitrogen nutrient‐replete and low‐nitrogen nutrient‐limited conditions. Across this temperature gradient, the competitive outcome under both nutrient conditions at any assay temperature, and the critical temperature at which competitive advantage shifted from one species to the other, was well predicted by the temperature dependencies of the growth rates of the two species measured in monocultures. The temperature at which the competitive advantage switched from P. tricornutum to T. pseudonana increased from 18.8°C under replete conditions to 25.3°C under nutrient‐limited conditions. Thus, P. tricornutum was a better competitor over a wider temperature range in a low N environment. Being able to determine the competitive outcomes from physiological responses of single species to environmental changes has the potential to significantly improve the predictive power of phytoplankton spatial distribution and community composition models.

Near real-time detection of abnormal vessels’ behaviours and vessel sourced pollution in Sri Lanka’s maritime zones: An investigation

The largest ecosystems on Earth are the oceans and it is essential to conserve and sustainably use these vital resources. Waste created by the activities on land and sea, leads to the destruction of the ecosystems. As Sri Lanka is an island in the Indian Ocean, with rights to a vast sea area that extends from the shores, it is mandatory to sustainably manage its marine environment. Regular, systematic reviews of the state of marine environment provide an understanding of the various aspects of marine environment change and the implications for sustainability. Space borne platforms provide Earth observation data collected by different types of sensors, at regular intervals for the management of Earth environment. Earth observation data acquired with Synthetic Aperture Radar (SAR) technology has become useful for the detection of marine pollution during the day and night, regardless of cloud covers. However, availability of near real-time data is important for prompt detection and response. Revisit time of a satellite is an important factor and satellite constellations are used to further improve revisit times, for example, Copernicus Sentinel-1 satellite constellation can provide SAR data with a high revisit time. The research aims to explore the use of near real-time Sentinel-1 SAR data with automated mechanisms, for information extraction that supports early detection of abnormal vessels’ behaviours and vessel sourced pollution in Sri Lanka’s maritime zones.

Two types of hyperthermal events in the Mesozoic-Cenozoic: Environmental impacts, biotic effects, and driving mechanisms

A deeper understanding of hyperthermal events in the Earth’s history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events are classified based on the characteristics of the carbon isotope excursion (CIE) of the five representative hyperthermal events in the Mesozoic and Cenozoic. The first type is overall characterized by negative CIEs (NCHE) and represented by the Permian-Triassic boundary event (PTB, ~252 Ma), the early Toarcian oceanic anoxic event (TOAE, ~183 Ma), and the Paleocene-Eocene Thermal Maximum event (PETM, ~56 Ma). The second type is overall characterized by positive CIEs (PCHE) and represented by the early Aptian oceanic anoxic event (OAE1a, ~120 Ma) and the latest Cenomanian oceanic anoxic event (OAE2, ~94 Ma). Hyperthermal events of negative CIEs (NCHE), lead to dramatic changes in temperature, sedimentation, and biodiversity. These events caused frequent occurrence of terrestrial wildfires, extreme droughts, acid rain, destruction of ozone layer, metal poisoning (such as mercury), changes in terrestrial water system, and carbonate platform demise, ocean acidification, ocean anoxia in marine settings, and various degree extinction of terrestrial and marine life, especially in shallow marine. In contrast, hyperthermal events of positive CIEs (PCHE), result in rapid warming of seawater and widespread oceanic anoxia, large-scale burial of organic matter and associated black shale deposition, which exerted more significant impacts on deep-water marine life, but little impacts on shallow sea and terrestrial life. While PCHEs were triggered by volcanism associated with LIPs in deep-sea environment, the released heat and nutrient were buffered by seawater due to their eruption in the deep sea, thus exerted more significant impacts on deep-marine biota than on shallow marine and terrestrial biota. This work enriches the study of hyperthermal events in geological history, not only for the understanding of hyperthermal events themselves, large igneous provinces, marine and terrestrial environment changes, mass extinctions, but also for providing a new method to identify the types of hyperthermal events and the inference of their driving mechanism based on the characteristics of carbon isotopic excursions and geological records.

Ocean acidification, hypoxia and warming impair digestive parameters of marine mussels

Global change and anthropogenic activities have driven marine environment changes dramatically during the past century, and hypoxia, acidification and warming have received much attention recently. Yet, the interactive effects among these stressors on marine organisms are extremely complex and not accurately clarified. Here, we evaluated the combined effects of low dissolved oxygen (DO), low pH and warming on the digestive enzyme activities of the mussel Mytilus coruscus. In this experiment, mussels were exposed to eight treatments, including two degrees of pH (8.1, 7.7), DO (6, 2 mg/l) and temperature (30 °C and 20 °C) for 30 days. Amylase (AMS), lipase (LPS), trypsin (TRY), trehalase (TREH) and lysozyme (LZM) activities were measured in the digestive glands of mussels. All the tested stress conditions showed significant effects on the enzymatic activities. AMS, LPS, TRY, TREH showed throughout decreased trend in their activities due to low pH, low DO, increased temperature and different combinations of these three stressors with time but LZM showed increased and then decreased trend in their activities. Hypoxia and warming showed almost similar effects on the enzymatic activities. PCA showed a positive correlation among all measured biochemical parameters. Therefore, the fitness of mussel is likely impaired by such marine environmental changes and their population may be affected under the global change scenarios.

Ocean surface current retrieval at Hangzhou Bay from Himawari-8 sequential satellite images

Ocean surface currents play a key role in the earth’s climate. They affect virtually all processes occurring in the ocean and can also directly affect many important socio-economic activities. Himawari-8 meteorological satellite has an international advanced geostationary orbit imager sensor, AHI, with high time resolution and spatial coverage, Himawari-8 can be used to observe the subtle changes in marine environments. In this study, we used Himawari-8 data received from the Joint Receiving Station for Satellite Remote Sensing of Xiamen University to retrieve coastal currents in Hangzhou Bay. Particularly, the Maximum Correlation Coefficient (MCC) and the Generalized Hough Transform (GHT) methods were used to retrieve them respectively The retrieved sea surface currents are analyzed and verified by the numerical model data of the Taiwan Strait current forecasting system (TFOR). The results show that (1) the Himawari-8 satellite data can be used to effectively estimate the ocean current; (2) The results of the two methods are in agreement with each other, and the error in the current measured using the GHT method is smaller in the Yangtze estuary and offshore areas, where the turbidity characteristic front is stronger.

An assessment of aluminum and iron in normalisation and enrichment procedures for environmental assessment of marine sediment

An increasing use of Al and Fe as normalising elements in assessment of anthropogenic change (metal enrichment) in marine environments has prompted the current study. This investigation was facilitated by a unique, large data set comprising total- and size-normalised sedimentary metals data from 41 estuaries (n = 3494) in central New South Wales, Australia. Total sediment Al and Fe concentrations varied substantially in these estuaries, even for samples comprising 100% fine fraction (ff), due to changes in the clay mineral mix and variable clay mineral chemistry. Normalising sedimentary metals to 100% ff produced variable results, however this approach improved markedly when samples with <10% ff was removed. The technique of normalising sedimentary metals by adjusting total Al to 50,000 μg/g considered to represent 100% ff was critically assessed. Results showed that total Al for 100% ff varied between estuaries and the most appropriate Al concentration for normalisation was the intercept value of the trend line in total Al vs ff bivariate plots and the 100% ff axis. It is recommended that, in the absence of size-normalised metals data, this intercept value be used as the normalising Al concentration, which should be determined locally for 100% ff. Iron was also assessed as a normalising element using the same approach and provided similar results, but was less attractive due to diagenetic alteration. The post-extraction normalisation (PEN) method provided valid, normalised metals data capable of estimating enrichment (magnitude of anthropogenic change) in marine environments.

Low-molecular-weight organic acids as important factors impacting seawater acidification: A case study in the Jiaozhou Bay, China

Low-molecular-weight organic acids (LMWOAs) are ubiquitous water-soluble organic compounds with mass production worldwide, but their influence on coastal marine environments is still lack of consideration. In this study, we select a typical nearshore bay - the Jiaozhou Bay, which is surrounded by Qingdao — a city with modern manufacture, agriculture, aquaculture and service industry, as study area, to investigate the effect of LMWOAs on the nearshore marine environment, and their impact on seawater acidification in coastal areas. During Sep. 2016 to Aug. 2017, we identified three different LMWOAs – acetic acid (AA), formic acid (FA) and lactic acid (LA), with average concentrations of 46.7, 13.9 and 1.4 μmol·L−1 in the seawater of the bay, respectively. Due to the establishment of the Jiaozhou Bay Bridge, the seawater exchange capacity was weakened and thereby the concentration and stocks of AA and FA increased. As weak acids in seawater, the influence of LMWOAs on the seawater acidification of the Jiaozhou Bay was investigated. LMWOAs had significant impact on seawater pH and every 10 μmol·L−1 LMWOA caused an average of 0.02 pH unit decrease. From 2010 to 2017, pH value in the seawater of the bay decreased by about 0.103 and LMWOAs contributed about 83% of its decrease. Besides, two models were established to estimate the influence of LMWOAs on the seawater pH by applying the data set of dissolved inorganic carbon (DIC), total alkalinity (TA) and LMWOAs. The results showed that LMWOAs could enhance acidification of coastal seawater. Considering the importance of LMWOAs in seawater, it is necessary to evaluate their future changes in coastal marine environments. This study initiated a way to identify the source of LMWOAs in seawater and to evaluate their contribution to seawater acidification, and also provided a series of dataset for future study on LMWOAs in coastal environment.

Lifeform indicators reveal large-scale shifts in plankton across the North-West European shelf.

Increasing direct human pressures on the marine environment, coupled with climate-driven changes, is a concern to marine ecosystems globally. This requires the development and monitoring of ecosystem indicators for effective management and adaptation planning. Plankton lifeforms (broad functional groups) are sensitive indicators of marine environmental change and can provide a simplified view of plankton biodiversity, building an understanding of change in lower trophic levels. Here, we visualize regional-scale multi-decadal trends in six key plankton lifeforms as well as their correlative relationships with sea surface temperature (SST). For the first time, we collate trends across multiple disparate surveys, comparing the spatially and temporally extensive Continuous Plankton Recorder (CPR) survey (offshore) with multiple long-term fixed station-based time-series (inshore) from around the UK coastline. These analyses of plankton lifeforms showed profound long-term changes, which were coherent across large spatial scales. For example, 'diatom' and 'meroplankton' lifeforms showed strong alignment between surveys and coherent regional-scale trends, with the 1998-2017 decadal average abundance of meroplankton being 2.3 times that of 1958-1967 for CPR samples in the North Sea. This major, shelf-wide increase in meroplankton correlated with increasing SSTs, and contrasted with a general decrease in holoplankton (dominated by small copepods), indicating a changing balance of benthic and pelagic fauna. Likewise, inshore-offshore gradients in dinoflagellate trends, with contemporary increases inshore contrasting with multi-decadal decreases offshore (approx. 75% lower decadal mean abundance), urgently require the identification of causal mechanisms. Our lifeform approach allows the collation of many different data types and time-series across the NW European shelf, providing a crucial evidence base for informing ecosystem-based management, and the development of regional adaptation plans.

Two-step extinction of Late Cretaceous marine vertebrates in northern Gulf of Mexico prolonged biodiversity loss prior to the Chicxulub impact

Recent studies on mass extinctions are often based on the global fossil record, but data from selected paleogeographic regions under a relatively constant paleoenvironmental setting can also provide important information. Eighty-nine marine vertebrate species, including cartilaginous and bony fish and marine reptiles, from northern Gulf of Mexico – located about 500 km from the Chicxulub crater – offer a unique opportunity to determine an extinction process during the last 20 million years of the Late Cretaceous. Our diversity data show two separate extinction events: (i) the ‘Middle Campanian Crisis’ (about 77 Mya) and (ii) the end-Maastrichtian (66 Mya) events. Whether this stepwise pattern of extinctions occurred locally or globally cannot be determined at present due to the lack of a dataset of the marine vertebrate record for reliable comparison. However, this stepwise pattern including the Middle Campanian and end-Maastrichtian events for, at least, a 13 million-year interval indicates long-term global marine environmental changes (e.g., regression, ocean water chemistry change). Because most Cretaceous marine vertebrates already disappeared in the Gulf of Mexico prior to the latest Maastrichtian, the Chicxulub Impact may not be considered as the most devastating extinction event for the community.

Estimation of the Particulate Organic Carbon to Chlorophyll-a Ratio Using MODIS-Aqua in the East/Japan Sea, South Korea

In recent years, the change of marine environment due to climate change and declining primary productivity have been big concerns in the East/Japan Sea, Korea. However, the main causes for the recent changes are still not revealed clearly. The particulate organic carbon (POC) to chlorophyll-a (chl-a) ratio (POC:chl-a) could be a useful indicator for ecological and physiological conditions of phytoplankton communities and thus help us to understand the recent reduction of primary productivity in the East/Japan Sea. To derive the POC in the East/Japan Sea from a satellite dataset, the new regional POC algorithm was empirically derived with in-situ measured POC concentrations. A strong positive linear relationship (R2 = 0.6579) was observed between the estimated and in-situ measured POC concentrations. Our new POC algorithm proved a better performance in the East/Japan Sea compared to the previous one for the global ocean. Based on the new algorithm, long-term POC:chl-a ratios were obtained in the entire East/Japan Sea from 2003 to 2018. The POC:chl-a showed a strong seasonal variability in the East/Japan Sea. The spring and fall blooms of phytoplankton mainly driven by the growth of large diatoms seem to be a major factor for the seasonal variability in the POC:chl-a. Our new regional POC algorithm modified for the East/Japan Sea could potentially contribute to long-term monitoring for the climate-associated ecosystem changes in the East/Japan Sea. Although the new regional POC algorithm shows a good correspondence with in-situ observed POC concentrations, the algorithm should be further improved with continuous field surveys.

Unraveling the choice of the north Atlantic subpolar gyre index

The north Atlantic subpolar gyre (SPG) has been widely implicated as the source of large-scale changes in the subpolar marine environment. However, inconsistencies between indices of SPG-strength have raised questions about the active role SPG-strength and size play in determining water properties in the eastern subpolar North Atlantic (ENA). Here, by analyzing various SPG indices derived from observations and a global coupled model, we show that the choice of the SPG index dictates the interpretation of SPG strength-salinity relationship in the ENA. Variability in geostrophic currents derived from observed hydrography and model based Lagrangian trajectories reveal zonal shifts of advective pathways in the ENA and meridional shifts in the western intergyre region. Such shifts in advective pathways are manifestations of variability in the size and strength of the SPG, and they impact salinity by modulating the proportion of subpolar and subtropical waters reaching the ENA. SPG indices based on subsurface density and principal component analysis of sea surface height variability capture these shifts in advective pathways, and are therefore best suited to describe SPG-salinity relationship in the ENA. Our results establish the dynamical constraints on the choice of the SPG index and emphasize that SPG indices should be cautiously interpreted.

Projections of changes in marine environment in coastal China seas over the 21st century based on CMIP5 models

The increases of atmospheric carbon dioxide and other greenhouse gases have caused fundamental changes to the physical and biogeochemical properties of the oceans, and it will continue to occur in the foreseeable future. Based on the outputs of nine Earth System Models from the fifth phase of the Coupled Model Intercomparison Project (CMIP5), in this study, we provided a synoptic assessment of future changes in the sea surface temperature (SST), salinity, dissolved oxygen (DO), seawater pH, and marine net primary productivity (NPP) in the coastal China seas over the 21st century. The results show that the mid-high latitude areas of the coastal China seas (East China Seas (ECS), including the Bohai Sea, Yellow Sea, and East China Sea) will be simultaneously exposed to enhanced warming, deoxygenation, acidification, and decreasing NPP as a consequence of increasing greenhouse gas emissions. The magnitudes of the changes will increase as the greenhouse gas concentrations increase. Under the high emission scenario (Representative Concentration Pathway 8.5), the ECS will experience an SST increase of 3.24±1.23°C, a DO concentration decrease of 10.90±3.92 µmol/L (decrease of 6.3%), a pH decline of 0.36±0.02, and a NPP reduction of −17.7±6.2 mg/(m2·d) (decrease of 12.9%) relative to the current levels (1980–2005) by the end of this century. The co-occurrence of these changes and their cascade effects are expected to induce considerable biological and ecological responses, thereby making the ECS among the most vulnerable ocean areas to future climate change. Despite high uncertainties, our results have important implications for regional marine assessments.

Analysis on the relationship between fisheries economic growth and marine environmental pollution in China's coastal regions

The rapid development of China's fisheries economy is accompanied by intensified marine environmental pollution over the period covered by this study. Based on data from multiple sources, this paper attempts to measure the relationship between fisheries economic growth and marine environmental pollution among China's coastal regions over the past 17 years. For this purpose, it firstly quantifies changes in fisheries economy and fisheries population. It then goes onto comparing the degree of changes in fisheries economy and marine environment. Finally, it depicts the relationship between fisheries added value (FAV) and polluted marine area (PMA) and between per capita net income of fishermen (PCNIF) and PMA ratio. Results suggest thati)the compound annual growth rate of FAV, FAV per capita, and fisheries population are 8.35%, 8.61%, and −0.24%, respectively;ii)the difference of FAV per capita increases significantly over time, while that of PMA and PMA ratio decreases moderately;iii)the relationship between FAV and PMA and between PCNIF and PMA ratio in all China's Seas and in the East China Sea show the same inverted N-shape while in the South China Sea inverted U-shape. In the Bohai and Yellow Sea, the former's relationship exhibits inverted U-shape, with the latter's N-shape.

Research on the Impact of Reclamation Project on the Marine Environment in the Dongjiang Area of Tianjin Port

With the development of cities and the continuous expansion of human activities, the impact of humans on nature has gradually become prominent. After the Industrial Revolution, the relationship between humans and nature has undergone a subtle change. Whether human beings actively interfere with nature or unconsciously influence the natural environment through behavioral facts, the progress of many human societies is accompanied by the consumption and damage of natural energy. At the same time, nature is also using facts to remind humans that the environmental degradation caused by excessive intervention will eventually affect humans themselves. This study collected 2003, 2012, 2016, and 2019 survey data of seawater quality and ecological environment near the Tianjin Dongjiang Port area. Through a single factor analysis method, we found that the marine environment changes in this area in recent years. The development of Tianjin’s urban area is closely related to the development of the port. At the same time, the sea reclamation project in Dongjiang may also be one of the reasons for this change. sea reclamation project in Dongjiang may also be one of the reasons for this change.

SEQUENCE STRATIGRAPHIC AND PALEOECOLOGIC ANALYSIS OF AN ALBIAN CORAL-RUDIST PATCH REEF, ARIZONA, USA

ABSTRACTFossilized reefs can preserve critical information about changes in marine environments over a relatively short period of time. The interpretation of these changes is often hindered by the complexity of reef growth with respect to architecture, biotic zonation, and time. High-resolution mapping and data collection incorporating both sequence stratigraphical and paleoecological principles are needed to document the architectural complexity of reef development. To demonstrate this, we present a case study in which both principles are integrated to build a new stratigraphic framework for an Albian-aged rudist-coral patch reef outcrop (Paul Spur, Bisbee, AZ, USA). The dataset reveals that the outcrop preserves five stages of development: (1) initial shoal deposition; (2) pioneer reef growth; (3) reef diversification; (4) reef hiatus; and (5) rudist shoal development. These stages represent periods of deposition and reef growth within high-frequency transgressive-regressive sequences. Interpretations of sedimentological and paleoecological data are then used to demonstrate the variable influence of different environmental controls on reef growth. Prevailing wind and current direction act as higher order controls on overall reef architecture by influencing windward-leeward asymmetry. Fluctuations in relative water depth as well as sedimentation rate, source, and type is an important influence on reef community and growth habit. Though corals and rudists cohabited during much of the reef's history, corals dominated when water depth was greater and external sediment influx lesser, whereas rudists dominated in shallow water depths and during periods of high external sediment influx. This work demonstrates that detailed evaluation of stratigraphy and paleoecology, as well as careful consideration of timelines and heterogeneity, is essential for building an accurate stratigraphic framework that allows a more thorough understanding of processes driving reef growth.

Land plant evolution decreased, rather than increased, weathering rates

Abstract The repeated evolution of trees is widely thought to have enhanced the capacity of silicate weathering via the impact of deep rooting. However, land plants are also responsible for wetland assembly and organic carbon burial. The total burial output of carbon via both organic and inorganic deposition must balance input to the exogenic system from volcanic outgassing on million-year time scales. Increased partitioning of carbon burial toward organic carbon and away from inorganic carbon reduces the marine carbonate burial flux, necessitating a lowered total flux of alkalinity to the oceans to maintain mass balance in the Earth’s surface carbon cycle. This flux includes the nutrient delivery from the terrestrial vegetation implicated as a driver of marine evolution, extinction, and environmental change including anoxia and black shale formation. Here, the burial of terrestrial organic carbon, first substantially in the Devonian and continuing through to the present, is argued to require a reduction in silicate weathering rates when compared to earlier times, given the independence of volcanic outgassing from weathering on short time scales. Land plants still may cause reductions in steady-state atmospheric CO2 levels, but via increasing the silicate weathering feedback strength, not silicate weathering rates. The mass-balance constraints on the long-term carbon cycle provide a mechanism for linking how land plant evolution simultaneously increased nutrient recycling and weathering efficiency of the Earth’s surface.