Response of Benthic Invertebrates to Disturbance From Stream Restoration: The Importance of Bryophytes

The response of benthic invertebrates to disturbance from stream restoration was studied in the Reinikankoski rapids, central Finland. I hypothesized that stream bryophytes could act as a refugium for invertebrates. The restoration procedure destroyed nearly half of the bryophytes present at the study reach, and invertebrate densities decreased sharply immediately after the restoration. Within 2 weeks, invertebrates had recolonized the disturbed reach, and within 1 month peak numbers were attained. Invertebrates showed a clear association with bryophytes, especially after the restoration. My study shows that invertebrate recovery can be relatively fast in winter, and underlines the importance of stream mosses as invertebrate habitat and refugia. They should be taken in consideration in stream restoration projects by leaving patches of stream bottom intact.     

Responses of five woody species to burial by marly sediment: the role of biomass allocation pattern flexibility

Aims In eroded lands of the French Southern Alps, burial of early established seedlings under marly sediment weakens the effect of vegetation on soil stabilization and sediment trapping. Therefore, this protective role is largely dependent on species' resistance to burial, and the understanding of species' tolerance to this environmental disturbance is highly valuable for basic knowledge on plant succession and for ecological restoration purposes.Methods The response of five woody species with contrasting ecological requirements and natural habitats—three tree species, Pinus nigra, Robinia pseudoacacia and Acer campestre, and two shrubs, Ononis fruticosa and Hippophae rhamnoides —to experimental burial under marly sediment was studied. Seedlings were exposed to three burial levels: no burial (control), partial burial (50% of seedling height) and complete burial (100% of seedling height). Burial tolerance was evaluated based on seedling survival, height and biomass. Biomass allocation to shoots and roots and soluble sugar and starch contents in roots and stems were measured to identify plant traits that determine species response to burial.Important findings All species survived partial burial but only A. campestre seedlings emerged from complete burial. Tree species were more tolerant to burial and buried plants showed no significant differences with control. The two shrubs were found less tolerant and buried plants showed slower growth than controls. The results showed that species response was not related to initial soluble and starch content in roots and stems, but instead to biomass allocation pattern flexibility.     

The Impact of Chemical Compounds on Benthic Invertebrates from the Danube and Danube Delta Systems

The aim of this study is to assess freshwater sediment in terms of biological and preliminary toxicological control linked to a series of variables along the Danube River and Danube Delta systems. The research is focused on eight points of the Romanian sector in the summer to autumn of 2012. Results show a high concentration of metals, pesticides, and petroleum products in sediment samples in the monitored period. The survey is designed to gauge the total chemical pollution effects on the composition, living, and growth of benthic organisms. To assess the toxic hazard of contaminated sediment samples, a microbiotest with meiobenthic ostracods Heterocypris incongruens was performed with evaluation of mortality and growth-inhibition percentages. The preliminary results showed an increase of sediment toxicity, in terms of growth inhibition (>80%), especially at Murighiol and Ivancea. The chemical pressures alongside the temporal conditions were important variables which affected benthic communities. Low benthic diversity was found in the Isaccea–St. Gheorghe Branch sector of the Danube River. In terms of ecological status, the study reveals that the Danube and Danube Delta ecosystem are eutrophic systems equilibrated for good ecological status.     

小叶锦鸡儿幼苗对沙埋的生态适应和生理响应

以中国半干旱地区固定、半固定沙地分布最广泛的灌木种之一小叶锦鸡儿(Caragana microphylla)为对象,于2010～2011年在内蒙古科尔沁沙地测定了不同深度沙埋下其幼苗的存活率、株高、渗透调节物质含量、保护酶活性和膜透性变化,探讨小叶锦鸡儿对沙埋的生理响应特征。结果显示:(1)与对照相比,当沙埋深度为小叶锦鸡儿幼苗株高的25%～75%时,存活率差异不显著;当沙埋深度为50%～75%时其存活率增加,但株高明显下降,沙埋对其生长具有抑制作用;当沙埋达到其株高100%时幼苗全部死亡。(2)不同沙埋深度对小叶锦鸡儿幼苗叶片细胞膜透性无显著影响,对沙埋深度为其株高25%时,叶片含水量增加,MDA含量下降,POD活性增强,细胞膜未受到伤害;沙埋深度为其株高50%～75%时,叶片含水量下降,MDA含量增加,但SOD和POD对细胞膜起到了协同保护作用,细胞膜也未受到损伤;沙埋深度为株高25%～75%情况下,细胞膜未受到损伤,可溶性糖和脯氨酸含量变化不明显。研究认为:小叶锦鸡儿幼苗只能耐受部分沙埋,完全沙埋则会导致其幼苗全部死亡,沙埋胁迫下可溶性糖和脯氨酸等渗透调节物质含量反应迟缓可能是其耐沙埋能力较弱的主要生理原因之一。     

Responses of Benthic Infauna to Large-Scale Sediment Disturbance in Corpus Christi Bay, Texas

Responses of benthic infauna to large scale disturbance by dredged material placement were studied at eight paired (placement and reference) areas in Corpus Christi Bay, Texas in 1995 and 1996. Total infaunal abundance, taxa richness, and the biomass of annelids and molluscs in placement areas no longer differed from that of reference areas approximately one year after placement. Annual secondary production for annelids and molluscs did not differ between placement and reference areas, however mean (± standard error) total annual secondary production at reference areas (53.6 ± 5.8 g AFDW/m²/yr) was greater than that of placement areas (26.2 ± 2.5 g AFDW/m²/yr) due to higher brittle star densities in reference areas. Differences in community structure between placement and reference areas returned to pre-placement levels one year after disturbance. The magnitude of changes in sediment grain size related to disturbance was positively correlated with the degree of convergence of placement area communities with pre-placement and reference communities. Sediment compaction was consistently associated with infaunal taxonomic composition (BIOENV) and increased linearly with time after disturbance. The use of the term “recovery” with reference to recolonization of dredging-related disturbance implies a return to pre-placement ecological conditions that are frequently neither a reality nor a practical expectation for areas that are subject to repeated disturbances. Our characterization of biological responses to dredged material disturbance targeted benchmarks that were linked to both pre-disturbance conditions and differences between disturbed and neighboring undisturbed areas and indicate that impacts persisted less than one year.     

樟子松幼树株高及其逆境生理指标对沙埋的响应特征

以3龄樟子松幼树为材料,2013年在科尔沁沙地研究了不同沙埋深度下其株高、叶片膜透性、渗透调节物质含量及保护酶活性变化,以揭示沙埋条件下樟子松幼树生长及其对逆境的生理响应特征。结果显示:(1)在沙埋深度低于株高以上2cm时被埋樟子松幼树能够正常生长,其株高和芽长均明显高于非沙埋对照,并以沙埋深度为株高的50%时增长幅度最大;当沙埋深度超过株高2cm以上时,虽然植株高度和芽长也较埋前有一定增长,但均低于对照,且所有处理植株均未破土,后来全部死亡。(2)所有沙埋处理的叶片可溶性糖含量均显著低于对照,而POD活性显著高于对照,可溶性蛋白质和脯氨酸含量也高于对照。(3)随沙埋深度增加,叶片相对含水量总体呈增加趋势,但大多数处理与对照差异不显著;丙二醛含量基本呈显著下降趋势,可溶性蛋白和脯氨酸含量先增加后下降,而大多数处理的膜透性与对照差异不显著;随着沙埋深度增加,叶片可溶性糖含量显著下降,SOD和POD活性均先增加后下降。(4)相关分析显示,樟子松幼树叶片膜透性变化与MDA含量变化相关性几乎为零,可溶性蛋白与脯氨酸含量呈显著正相关关系,可溶性糖含量与脯氨酸含量呈显著负相关关系。研究表明,沙埋深度低于樟子松株高以上2cm能够促进其幼树生长;沙埋并没有导致樟子松幼树体内的膜脂过氧化,也没有引起细胞膜的损伤,在受到沙埋胁迫时,樟子松幼树体内SOD、POD以及可溶性蛋白和脯氨酸分别在防止其膜脂过氧化和维持细胞膨压中起到重要作用,而可溶性糖含量在沙埋过程中没有起到渗透调节作用。     

Responses of Deep‐Sea Meiobenthic Communities to Sediment Disturbance Simulating Effects of Polymetallic Nodule Mining

During a benthic impact experiment (BIE) carried out during 1995–1997 by the Interoceanmetal Joint Organization (IOM) at an abyssal site in the North‐East Pacific, sediment disturbance mimicking that resulting from polymetallic nodule extraction was created with a specialised device (the Benthic Disturber). The effects of the disturbance on meiobenthic communities were assessed immediately after disturbance and 22 months later. A reduction in meiobenthos abundance, observed immediately following impact, was not significant; neither were changes in composition of the meiobenthos which was dominated by nematodes and harpacticoids. The lack of any significant numerical response is probably accounted for by the moderate degree of disturbance in this study, compared with other BIE‐type experiments. On the other hand, statistically significant changes in both meiofauna abundance and vertical distribution profiles in the changed sediment within the Disturber tracks were recorded. After 22 months, a significant increase in overall meiobenthos abundance was detected in that part of the test site affected by increased resuspended sediment settlement and receiving natural phytodetrital inputs. Certain taxon‐specific responses on the part of nematodes and harpacticoids were noted both immediately after the disturbance and 22 months later. They were explained by the effects of sediment physical reworking and responses to phytodetrital enrichment. The results presented should aid in developing experimental designs, on both temporal and spatial scales, of future deep‐sea tests aimed at assessing the scale and consequences of man‐made impacts.     

The mobile epifauna of the soft bottoms in the subtidal Oosterschelde estuary: structure,function and impact of the storm-surge barrier

Data on the mobile epifauna of the Oosterschelde estuary, collected by beam trawl, were compiled from several studies. Multivariate statistical techniques brought out the fact that the Oosterschelde, when compared with neighbouring areas, has a characteristic epibenthic fauna. Diversity as measured by Hill's diversity numbers N through N ₊ , is higher for the Oosterschelde (N₁ = 4.5) than for the Voordelta (N₁ = 3.5) and the Westerschelde (N₁ = 2.2).Four epifaunal communities can be distinguished within the Oosterschelde, the two most seaward communities being the richest. Annual production is estimated at about 6 gADW m^–2 yr^–1, annual consumption is estimated at over 25 gADW m^–2 yr^–1. These results are highly dependent on the assumptions. Over 85% of the epibenthic production and consumption in the Oosterschelde is accounted for by only six species: starfish Asterias rubens, plaice Pleuronectes platessa, bib Trisopterus luscus, brown shrimp Crangon crangon, shore crab Carcinus maenas and dab Limanda limanda. In spite of its abundance, the sand goby Pomatoschistus minutus contributes little to the production.From the available data it is difficult to assess the impact of the construction of the storm-surge barrier and the compartmentalization dams on the epibenthic fauna. The increase in flatfish in the Hammen area is probably linked to the decrease in current velocities in that area. On the other hand the increase in the gadoids bib and whiting Merlangius merlangus is predominantly due to the stronger year classes in the post-barrier time period. Lower nutrient inputs through the Northern branch, in combination with the increase of the gadoids, may have caused the decline of the brown shrimp in the Oosterschelde. A decrease has also been observed in the sandeel Ammodytes tobianus and the hooknose Agonus cataphractus.     

Coral habitat in the Aleutian Islands of Alaska: depth distribution, fine-scale species associations, and fisheries interactions

The first in situ exploration of Aleutian Island coral habitat was completed in 2002 to determine the distribution of corals, to examine fine-scale associations between targeted fish species and corals, and to investigate the interaction between the areas’ diverse fisheries and coral habitat. Corals, mostly gorgonians and hydrocorals, were present on all 25 seafloor transects and at depths between 27 and 363 m, but were most abundant between 100 and 200 m depth. Mean coral abundance (1.23 colonies m⁻²) far exceeded that reported for other high-latitude ecosystems and high-density coral gardens (3.85 colonies m⁻²) were observed at seven locations. Slope and offshore pinnacle habitats characterized by exposed bedrock, boulders, and cobbles generally supported the highest abundances of coral and fish. Overall, 85% of the economically important fish species observed on transects were associated with corals and other emergent epifauna. Disturbance to the seafloor from bottom-contact fishing gear was evident on 88% of the transects, and approximately 39% of the total area of the seafloor observed had been disturbed. Since cold-water corals appear to be a ubiquitous feature of seafloor habitats in the Aleutian Islands, fisheries managers face clear challenges integrating coral conservation into an ecosystem approach to fisheries management.     

Enzyme Mechanisms in Temperature and Pressure Adaptation of Off-Shore Benthic Organisms: The Basic Problem

SYNOPSIS: The degree of participation of any given enzyme reactionin metabolism is not determined by energy-volume relationships,but rather by enzyme affinities for key regulatory ligands.In temperature adaptation, enzyme-substrate affinities oftendecrease as thermal kinetic energy increases, thus compensatingfor temperature-induced changes in reaction velocity at lowsubstrate concentrations. Since the effects of pressure arenot unidirectional (some enzymes are accelerated; some are unaffected;some are decelerated), a more functional solution in pressureadaptation is to elaborate enzymes whose affinities for keymetabolites are pressure independent. In consequence, at physiologicalsubstrate concentrations, the pressure sensitivities of catalysisand control of catalysis are probably held at a minimum.     

Effects of Sediment Fertilization and Burial on Cymodocea nodosa Transplants; Implications for Seagrass Restoration Under a Changing Climate

Sediment fertilization is recommended for improving seagrass restoration efforts, but few studies have evaluated the efficacy of such practice. Increasing storm frequency due to global change could lead to greater sediment mobilization. Understanding how this alteration will interact with fertilization to affect transplants is essential for future restoration planning. We examined the individual and combined effects of nutrients (ambient vs. repeated addition) and burial (control vs. increased frequency and intensity) on the performance and biomass partitioning of transplants of the seagrass Cymodocea nodosa at two sites within a north‐western Mediterranean meadow. Fertilization stimulated the production of shoots, total biomass, and branching. Burial increased leaf sheath length in one site while reduced shoot number, leaf number, leaf sheath length, total biomass, net shoot gain, and root‐to‐shoot ratio in the other site. Regardless of the site, fertilization and burial interaction reduced the length of vertical internodes and horizontal rhizomes, and the net shoot gain. Our research demonstrates that sediment fertilization ensures rapid colonization of restoration sites, providing C. nodosa plants up to eight times larger than controls in one growing season. However, it also indicates that interaction of increased burial and nutrients reduced the gain in terms of vegetative expansion and depressed vertical growth, making plants more vulnerable to subsequent disturbances. Therefore, seagrass restoration practitioners should account for changes in sediment elevation at transplanting sites when planning restoration programs and carefully evaluate the opportunity of applying fertilizers in sites subjected to greater sediment accumulation to avoid failure.     

Buried Alive: The Behavioural Response of the Mussels,Modiolus modiolus and Mytilus edulis to Sudden Burial by Sediment

Sedimentation in the sea occurs through natural processes, such as wave and tidal action, which can be exacerbated during storms and floods. Changes in terrestrial land use, marine aggregate extraction, dredging, drilling and mining are known to result in substantial sediment deposition. Research suggests that deposition will also occur due to the modern development of marine renewable energy. The response to individual burial under three depths of sediment, three sediment fractions and five burial durations was investigated in two mussel species, Modiolus modiolus and Mytilus edulis in specialist mesocosms. Both mussel species showed substantial mortality, which increased with duration of burial and burial by finer sediment fractions. M. modiolus was better able to survive short periods of burial than M. edulis, but at longer durations mortality was more pronounced. No mortality was observed in M. modiolus in burial durations of eight days or less but by 16 days of burial, over 50% cumulative mortality occurred. Under variable temperature regimes, M. edulis mortality increased from 20% at 8°C to over 60% at 14.5 and 20°C. Only M. edulis was able to emerge from burial, facilitated by increased byssus production, laid mostly on vertical surfaces but also on sediment particles. Emergence was higher from coarse sediment and shallow burials. Byssus production in M. edulis was not related to the condition index of the mussels. Results suggest that even marginal burial would result in mortality and be more pronounced in warm summer periods. Our results suggest that in the event of burial, adult M. modiolus would not be able to emerge from burial unless local hydrodynamics assist, whereas a small proportion of M. edulis may regain contact with the sediment water interface. The physiological stress resulting in mortality, contribution of local hydrodynamics to survival and other ecological pressures such as mussels existing in aggregations, are discussed.     

Watershed Effects on Chemical Properties of Sediment and Primary Consumption in Estuarine Tidal Flats: Importance of Watershed Size and Food Selectivity by Macrobenthos

Particulate organic matter transported from rivers to estuaries (POM_R) varies quantitatively and qualitatively across estuaries; however, a lack of comparative studies poses a challenge in general understanding of responses of estuarine food webs to POM_R input. We studied 20 estuarine tidal flats of the Pacific Northwest coast of North America, with watershed areas ranging from 7 to 8000 km². We used carbon-stable isotope (δ¹³C) to test the hypothesis that the nutritional contribution of POM_R to macrobenthos is proportional to relative abundances of POM_R in tidal flat sediments. The predominant origin of total POM (TPOM) in tidal flat sediments generally shifted from marine-origin POM (POM_M) to POM_R as watershed area increased; however, terrestrial-origin POM_R with high C/N predominated sediment TPOM even in estuaries with small watershed areas. Some macrobenthos species assimilated POM sources in proportion to sediment TPOM composition, and incorporated POM_R in POM_R-predominant sediments. These species were considered to have low food selectivity; however, the relative nutritional contribution of POM_R to these macrobenthos was still lower than the fraction of POM_R in sediment TPOM. Other species disproportionately utilized POM_M and/or benthic microalgae regardless of the relative abundance of POM_R, indicating their high food selectivity. The species-specific, low- or high-food selectivity was likely linked with deposit-feeding and filter-feeding, respectively. Hence, our hypothesis was supported conditionally. Our findings indicate that watershed area, relative abundance of POM_R in an estuary, and food selectivity of estuarine species are key factors controlling the tightness of linkage between watersheds and estuarine food webs.     

Detritus and Epibiota on Artificial Substrata: The Possible Role of Food in Structuring Hawaiian Epiphytal Amphipod Communities

Epiphytal amphipods prefer artificial substrata (bottle brushes) which accumulated epibiotic coatings while submerged in the sea for a period of up to 15 days. There is evidence that these amphipods eat epibiota on algae (predominately Padina japonica YAMADEA 1931 and Dictyota crenulata AGARDH 1847) and that food availability may be a factor which helps structure epiphytal amphipod communities.     

玉米对渗透胁迫的反应和生理适应

利用不同渗透势的培养液模拟土壤干旱条件,研究了玉米杂交种“中单2号”在此条件下的生长和生理的变化。实验表明,各指标对于渗透胁迫的变化敏感性顺序为叶片延伸速率、叶水势、脯氨酸含量>净光合速率>相对透性。玉米幼苗在渗透胁迫下具有一定的生理适应能力,表现在一定的渗透胁迫范围内随胁迫时间的延长,生长、生理变化有趋于缓和或恢复的趋势。     

Forms and Mobility of Sediment Phosphorus in Shallow Eutrophic Lake Võrtsjärv (Estonia)

The surficial sediment (0–10 cm) of shallow eutrophic Lake Võrtsjärv (Estonia) was characterized by an acid insoluble residue of 50% dry weight and low nutrient, Fe and Mn content. Among phosphorus (P) fractions (Hieltjes and Lijklema , 1980), NaOH-NRP amounted on an average to 50%, HCl-RP to 30%, NaOH-RP to 16%, and NH₄Cl-RP to 4% of their sum. Seasonal changes in sediment P content were inconsistent with mass balance calculations and could be attributed to sediment redistribution caused by decreasing water level. High Fe/P ratio (26–30) and the aeration of surficial sediment by frequent resuspension kept phosphate adsorbed. Low pore-water SRP (commonly <10 μg l⁻¹) usually prevented phosphate release from surficial sediment. However, a storm in September 1996 (max. wind speed 16 m s⁻¹) which coincided with the extremely low water level in the lake (mean depth 1.44 m), denuded deeper anoxic sediment layers and caused a SRP release of 193 mg P m⁻² d⁻¹.     

Recruitment of Planktonic Dinoflagellates: Importance of Benthic Resting Stages and Resuspension Events

Many factors have ken put forward to account for the development of nuisance phytoplankton blooms in coastal zones. Usually hydrological factors as temperature or salinity stratification and adequate nutrient and trace metal availability are held responsible for the phenomenon. The most frequent causative organisms for nuisance blooms are dinoflagellates, many of which have a dormant stage (resting cyst) in their life cycle. The role of the complex life-strategies of these forms in initiating bloom formation is the focus of this study. Special attention is given to 25 different dinoflagellate resting cyst types isolated from recent German North Sea and Baltic Sea sediments, and their germination frequency under different environmental conditions. Also, the role of cyst resuspension in relationship to the timing, persistence and recurrence of dinoflagellate blooms is extensive discussed.