High Shoot Density Research Articles

Influence of Water Temperature Anomalies on the Growth of Zostera marina Plants Held Under High and Low Irradiance Levels

Coastal water temperature anomalies are expected to intensify during the current period of global climate change. Sudden water temperature elevation (e.g., heat waves) or decrease (e.g., summer upwelling) can have a far-reaching influence on seagrasses in temperate regions. We examined the influence of anomalously elevated and decreased water temperatures on the growth of Zostera marina plants held under two different levels of irradiance. Core samples of wild Z. marina shoots were cultured under either suddenly elevated (from the in situ level of 20 to 27 °C during the fall experiment) or decreased (from the in situ level of 27 to 20 °C during the summer experiment) temperature. We included light as an experimental factor because the light requirements of seagrasses increase when plants are under thermal stress. The growth of Z. marina shoots under anomalously elevated water temperature conditions, which simulated marine heat waves, was significantly declined, whereas the plant growth under suddenly decreased water temperature conditions, which simulated summer upwelling events, was maintained or slightly increased. In the fall 2014 experimental period, Z. marina shoots under the suddenly elevated water temperature condition (27 °C) showed significant decreases in shoot density, biomass, and leaf productivity by ca. 40–80%, whereas plants held under the ambient water temperature condition (20 °C) maintained or slightly increased their growths. In the summer 2015 experimental period, Z. marina under the sudden temperature reduction conditions (20 °C) maintained relatively high shoot density and leaf productivity, whereas plants under the in situ high water temperature condition (27 °C) showed significantly reduced growths. The growth of Z. marina shoots, which were cultured in the optimal temperature condition (20 °C), was enhanced by increasing underwater irradiance. However, the adverse effects of high water temperature on Z. marina growth could not be reversed by increasing irradiance levels at the end of the experiments. According to the results of this study, the intensified sea surface water temperature anomalies induced by global climate change will alter the growth and distribution of temperate seagrasses and, consequently, the structure and function of the coastal seagrass ecosystems in the temperate region.

Eelgrass structural complexity mediates mesograzer herbivory on epiphytic algae

Structural complexity mediates ecological processes such as predation, competition, and recruitment in marine systems, but relatively little is known about its effects on herbivory. In temperate seagrasses, such as eelgrass (Zostera marina), the primary herbivores are small crustacean and gastropod mesograzers that promote seagrass persistence by preferentially consuming competing epiphytic algae. We used a laboratory grazing experiment, a field colonization experiment, and stable isotope analysis to determine whether one component of eelgrass structural complexity, shoot density, dictates the strength of mesograzer top-down effects on epiphytic algae, and whether this is influenced by mesograzer community composition. Our results suggest that increasing structural complexity shifted eelgrass communities from a bottom-up to a top-down controlled system. In the lab, mesograzers reduced epiphyte standing stock only in high-shoot density experimental communities, though grazing impact varied among different combinations of dominant mesograzer taxa. In our field experiment, epiphyte biomass was inversely correlated with mesograzer density in high but not in low-shoot density eelgrass plots. High-shoot density plots contained lower epiphyte biomass despite housing lower densities of mesograzers, when compared to low-density plots, suggesting potential effects of mesograzer behavior, community composition, or self-shading on epiphyte growth. Our results suggest that structural complexity can strongly influence rates of top-down and bottom-up processes in eelgrass habitat, and should be incorporated into future experiments on the role of herbivores in seagrass ecosystems.

Species diversity and distribution of seagrasses from the South Andaman, Andaman and Nicobar Islands, India

AbstractA survey was conducted with the objective to study seagrass distribution, bed size and shoot density in different substrata of the South Andaman Islands. A total of 231 seagrass sites were observed during the study, in which a total of eight species were found. The South Andaman region exhibited the highest species diversity followed by Havelock, Little Andaman and Neil Islands. Eleven continuous seagrass bed were noted during the study which were confined to three different types of substrata: sand only; sand mixed with coral sand and coral rubble; sand mixed with mud.Thalassia hemprichiiandCymodocea rotundatawere found in dense canopies and covered large areas associated with sand and coral rubble.Halophila beccariishowed moderate abundance in muddy substrata andHalodulespp. grew in fine sand. The highest shoot density was recorded at Haddo, followed by Vijaya Nagar and Chidyatapu, contributed mostly byHalodulespp. In general, seagrass diversity and distribution were mainly influenced by the percentage composition of sand. The authors recommend that the seagrass meadow of Haddo should be considered for conservation priority because of multiple anthropogenic pressures, such as sewage input, dumping of solid wastes on the shoreline and anchoring of boats.

Effects of Seed Treatments, Delayed Planting and Groundwater Levels on the Restoration of Sedge Meadows

Using a complete factorial, randomized block design, the effects of seed density (430 or 860 seeds/m2), seed stratification (stratified, non-stratified), split planting (complete seed mix planted in spring vs. non-aggressive species in spring and aggressive species in fall), and distance to groundwater (−5 or − 30 cm) were studied in a mesocosm complex in central Iowa. All 16 treatment combinations were replicated 5 times for a total of 80 mesocosms. The seed mix sown contained 25 species. At the end of the study, groundwater levels had the greatest effect on species richness, total shoot density, and total biomass. Seed stratification, seed density and delayed planting all had a significant impact on species richness and total shoot density. Delaying the planting of aggressive species significantly increased total shoot densities and biomass of non-aggressive species. Of the 20 species actually found in the mesocosms, 12 had higher shoot densities in the delayed planting, 11 in the high groundwater, 7 in the stratified seed, and 3 in the high seed density treatment. Overall, groundwater level and delayed planting of aggressive species had the largest impact on species diversity and shoot density.

Distribution and relative predation risk of nekton reveal complex edge effects within temperate seagrass habitat

Edge effects may be important drivers of community dynamics across marine habitat mosaics. Past research has consistently suggested that within temperate and sub-tropical seagrass habitats, organisms inhabiting meadow edges experience lower survivorship, presumably correlated with increased predation. However, these survivorship trends have not consistently translated to differences in faunal densities between edge and interior regions of seagrass meadows. We evaluated the evidence of edge effects on predation upon two dominant mesopredators within temperate eelgrass (Zostera marina) communities of the U.S. East Coast: blue crabs (Callinectes sapidus) and pinfish (Lagodon rhomboides). We considered three lines of data to arbitrate the null hypothesis that edge has no impact on distribution or predation on blue crabs or pinfish: (1) relative density as measured by catch-per-unit-effort (CPUE) of blue crabs and pinfish within edge (<1 m from unstructured sandflat boundaries) versus interior (>3 m from unstructured sandflat boundaries) regions of eelgrass meadows; (2) distribution of acoustically tagged red drum (Sciaenops ocellatus), a recognized predator of both blue crabs and pinfish, within eelgrass meadows (at 1-m bin resolution); and (3) relative mortality of tethered blue crabs and pinfish within edge versus interior regions of eelgrass meadows. Additionally, we manipulated seagrass shoot density to evaluate potential interactions between local habitat complexity and edge effects. We found no statistically detectable difference in catch rates of blue crabs or pinfish in edge versus interior habitats, and red drum detection frequencies were statistically indistinguishable moving from the seagrass-sandflat boundary toward the meadow interior. Despite these findings, we did record statistically and ecologically significant edge effects on predation rates of tethered blue crabs and pinfish. Counter to previous work, we found that blue crabs survived >2.5× longer, and pinfish survived >2× longer, along the meadow edge relative to interior. Furthermore, the strength of these predation-related edge effects was most notable for blue crabs within plots with higher shoot density, while the opposite pattern was true for pinfish. These findings are, in part, consistent with the dichotomy apparent in the seagrass literature with respect to edge effects on faunal density and survivorship. Additionally, our work provides new detail on how habitat edges may affect the population ecology of larger bodied, more mobile mesopredator species that have not received as much attention in previous studies (i.e., higher survivorship possible along edges).

Latitude, temperature, and habitat complexity predict predation pressure in eelgrass beds across the Northern Hemisphere.

Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 37° of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas insitu water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simply increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in predation intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.

Phytostabilization of heavy metals by the emergent macrophyte Vossia cuspidata (Roxb.) Griff.: A phytoremediation approach

ABSTRACTThe present study was conducted to investigate the potential of Vossia cuspidata as a phytoremediator to accumulate heavy metals from polluted water bodies. Thirty-two quadrats, distributed equally in eight sites (six polluted sites along the Ismailia canal and two unpolluted sites along the Nile River) were selected seasonally for plant, water, and sediment investigations. Winter plants recorded the highest values of shoot height, diameter, and leaf width, but the lowest shoot density. Plants collected in autumn had the lowest values of leaf length, width, and area, while those collected in spring had the highest shoot density, with the lowest shoot height. Summer populations had the highest fresh and dry plant biomass, while winter plants had the lowest. Fresh production and dry biomass of V. cuspidata in the unpolluted Nile were significantly higher than those in polluted canals. Chlorophyll a and carotenoid concentrations were reduced under pollution stress. Spring plants accumulated the highest concentrations of Cr, Cu, and Pb in their root, and the lowest concentrations of Al, Cd, Cr, and Zn in their shoot. The bioaccumulation factor for most investigated metals, except Al, Cr, and Fe was greater than 1, while the translocation factor of all metals was less than 1, therefore this plant is considered to be a potential for these metals phytostabilization.

Metal uptake capability of Cyperus articulatus L. and its role in mitigating heavy metals from contaminated wetlands.

Wetland plants are biological filters that play an important role in maintaining aquatic ecosystem and can take up toxic metals from sediments and water. The present study investigated the seasonal variation in the accumulation potential of heavy metals by Cyperus articulatus in contaminated watercourses. Forty quadrats, distributed equally in 8 sites (six contaminated sites along Ismailia canal and two uncontaminated sites along the River Nile), were selected seasonally for sediment, water, and plant investigations. Autumn was the flourishing season of C. articulatus with the highest shoot density, length, and diameter as well as aboveground biomass, while summer showed the least growth performance. The photosynthetic pigments were markedly reduced under contamination stress. C. articulatus plants accumulated concentrations of most heavy metals, except Pb, in their roots higher than the shoots. The plant tissues accumulated the highest concentrations of Fe, Cd, Ni, and Zn during autumn, while Cu and Mn during spring, and Cr and Co during winter. It was found that Cd, Cu, Ni, Zn, Pb, and Co had seasonal bioaccumulation factor (BF)>1 with the highest BF for Cd, Ni, and Zn during autumn, Co, Cu, and Pb in winter, spring, and summer, respectively. The translocation factor of most heavy metals, except Pb in spring, was <1 indicating potential phytostabilization of these metals. In conclusion, autumn is an ideal season for harvesting C. articulatus in order to monitor pollution in contaminated wetlands.

Evaluation of warm season turfgrasses for various qualitative and quantitative traits under Gujarat agro-climatic conditions

An experiment was carried out to evaluate different turfgrass species and varieties for the morphological characters under south Gujarat agro-climatic condition. Wide range of variation among the 13 genotypes of turfgrasses was recorded with respect to bio-agronomical and quality characteristics. Among the various characters, minimum days to 90 per cent establishment and deepest root were observed in Cynodon dactylon Local, which was at par with C. dactylon × C. transvaalensis Tifdwarf. Lowest canopy height, shortest average stolon internodal diameter, highestshoot density, narrowest leaf width and slowest VLGR were recorded in Zoysia tenuifolia. Maximum cumulative fresh clipping yield and minimum value of stolon internodal length were registered in Tifdwarf. Z. tenuifolia, Z. matrella and Tifdwarf showed very fine texture of leaves, whereas the latter also showed consistently good average turf quality rating and chlorophyll content in the whole period of experimentation. Under south Gujarat agro-climatic condition, C. dactylon L. × C. transvaalensis Tifdwarf performed best in most of turf quality parameters and can be subjected to further functional quality trials for sports and athletic turf.

Architectural characteristics of six olive cultivars with respect to their suitability for high density orchards

In a high density (1,250 trees ha-1) olive orchard in central Italy, the architectural characteristics of 'Arbequina', 'Arbosana', 'Koroneiki', 'FS17', 'Don Carlo' and 'Giulia' cultivars was studied. Tree height, canopy dimensions, trunk diameter at 0.20, 0.75, 1.5, 2.0 m from the ground, branch intersection height along the trunk, diameter and length of the primary branches were measured in 2010, when trees were 2-year-old. On sampled branches at different height, all the productive and vegetative shoots were spatially described. Tree height, trunk diameter and canopy volume were not significantly different among cultivars, while the number of primary branches was lower in 'FS17' compared to 'Arbequina', 'Arbosana' and 'Koroneiki'. The studied cultivars had different branching patterns along the trunk: a low density between 1 and 1.5 m trunk height in 'FS17' and a high between 1.5 and 2.0 m in 'Arbequina'. Moreover, the length/diameter ratio of the primary branches was low and high in 'Arbosana' and 'Giulia' and in 'Arbequina', respectively. 'Arbequina' also showed a uniform shoot density along the main axis of the primary branch, whereas an alternate shoot density with the presence of empty portions was observed in the other cultivars. A higher shoot density in the medium-proximal portion of the branch was seen for 'Arbosana' and 'FS17'. Results presented in this study supply helpful information about the different canopy and branch architectural characteristics of the six studied olive cultivars with respect to their suitability to high density plantations.

Evaluation of the Productivity of Vertical Oil Wells by Using Different High Shot Density (HSD) Guns

This work explains how to evaluate the different perforation parameters of the production vertical oil wells by using well test reservoir description and perforation information The necessary data have been collected from Hungarian oil wells including reservoir description data from the MOL Company files Four vertical oil wells have been evaluated The perforating guns data collected from the Schlumberger Company Four perforating HSD guns were used with different charge and explosive load design nbsp In this study calculation method used to determine the perforation depth the influence of the different composite skin effect damage skin factor crushed zone skin factor and the perforation skin factor than we evaluate the flow rate of the different kind of guns We consider the most important parameters influence the productivity of the perforated vertical oil wells We obtained the relationship between the perforation depth and the skin factor the perforation depth and the flow rate the skin factor and the flow rate and we identify the different flow rate After giving the detailed figures and results we evaluate the results of the perforation work In this work we proved that there is calculation method by which the flow rate of the vertical oil well can be estimated before the perforating To have the best flow rate we should choose the right design of the perforation gun Hungarian oil wells will improved their productivity by using high shut density guns Flow rate evaluation needs a good knowledge of rock properties and flow properties

Evaluation of the Productivity of Vertical Oil Wells by Using Different High Shot Density (HSD) Guns

Evaluation of the Productivity of Vertical Oil Wells by Using Different High Shot Density (HSD) Guns

Limited effects of source population identity and number on seagrass transplant performance.

Global declines in coastal foundation species highlight the importance of effective restoration. In this study, we examined the effects of source population identity and diversity (one vs. three sources per plot) on seagrass (Zostera marina) transplant success. The field experiment was replicated at two locations in Massachusetts with adjacent natural Zostera marina beds to test for local adaptation and source diversity effects on shoot density. We also collected morphological and genetic data to characterize variation within and among source populations, and evaluate whether they were related to performance. Transplants grew and expanded until six months post-transplantation, but then steadily declined at both sites. Prior to declines, we observed variation in performance among source populations at one site that was related to morphological traits: the populations with the longest leaves had the highest shoot densities, whereas the population with the shortest leaves performed the worst at six months post-transplantation. In addition, multiple source plots at this same transplant site consistently had similar or higher shoot densities than single source plots, and shoots from weak-performing populations showed improved performance in multiple source plots. We found no evidence for home site advantage or benefits of population-level genetic variation in early transplant performance at either site. Our results show limited effects of source population on early transplant performance and suggest that factors (e.g., morphology) other than home site advantage and population genetic variation serve a role. Based on our overall findings that transplant success varied among source populations and that population diversity at the plot level had positive but limited effects on individual and plot performance, we support planting shoots from multiple source sites in combination to enhance transplant success, particularly in the absence of detailed information on individual source characteristics.

Does selection for gamete dispersal and capture lead to a sex difference in clump water-holding capacity?

Differences in male and female reproductive function can lead to selection for sex-specific gamete dispersal and capture traits. These traits have been explored from shoot to whole plant levels in wind-pollinated species. While shoot traits have been explored in water-fertilized species, little is known about how whole plant morphology affects gamete dispersal and capture. We used the dioecious, water-fertilized plant Bryum argenteum to test for differences in clump morphology and water-holding characteristics consistent with divergent selection. We hypothesized that sex-specific clump morphology, arising at maturity, produces relatively low male water-holding capacity for gamete dispersal and high female capacity for gamete capture. We measured isolated young shoot and clump water-holding capacity and clump morphological characteristics on greenhouse-grown plants. Young shoot capacity was used to predict clump capacity, which was compared with actual clump capacity. Young male shoots held more water per unit length, and male clumps had higher shoot density, which extrapolated to higher clump water-holding capacity. However, female clumps held more water and were taller with more robust shoots. Actual clump capacity correlated positively with clump height and shoot cross-sectional area. The sex difference in actual clump capacity and its unpredictability from younger shoots are consistent with our hypothesis that males should hold less water than females to facilitate sexual reproduction. These results provide conceptual connections to other plant groups and implications for connecting divergent selection to female-biased sex ratios in B. argenteum and other bryophytes.

Comparative performance of warm season turfgrass varieties under Delhi conditions

The present investigation was carried out at Division of Floriculture and Landscaping, Indian Agricultural Research Institute, Pusa, New Delhi. The experiment was laid out in randomized block design (RBD) with three replications and seven treatments consisting of six varieties (viz. Selection 1, Bargusto, Panama, Panam, Palma and Tifdwarf 419) and Paspalum notatum species. These were evaluated for their suitability to be used as turfgrass under Delhi conditions. The suitability was evaluated on the basis of different morphological, physiological and biochemical traits. Out of evaluated varieties and species, Tifdwarf 419 exhibited better performance with respect to shoot dry weight (2.03 g/ 100 cm2), shoot fresh weight (5.78 g/100 cm2), root length (17.17 cm), root density (35.00 number/100 cm3), relative water content (86.96 %), chlorophyll a (2.63 mg/g fresh weight), chlorophyll b (0.53 mg/g fresh weight) and total chlorophyll (3.24 mg/g fresh weight) when compared to other varieties. Apart from these characteristics, short shoot length of 6.07 cm and high shoot density (331.27 number/100 cm2 area), along with good colour throughout the growing season was observed in Tifdwarf 419. Selection 1 also showed desirable shoot fresh weight (5.07 g/100 cm2), root length (16.10 cm), root density (28.87 number/100 cm3) and shoot density (395.40 number/100 cm2 area). The Cynodon dactylon varieties Tifdwarf 419 and Selection 1 were found to be most suitable to be used as turfgrasses in Delhi conditions.

Gamma-ray Irradiation Induces Useful Morphological Variation in Bermudagrass

Bermudagrass, Cynodon dactylon (L.) Pers. is a widely used warm-season turfgrass species in warmer regions of the world. Gamma (ɣ) irradiation has been used to generate useful variations in turfgrass breeding for various morphological traits. The objective of the present study was to measure and determine variations in morphology and turfgrass characteristics of a native drought resistant bermudagrass germplasm irradiated with 70, 90 or 110 Gy using a 60Co source. The stolons containing a single node were irradiated and immediately planted for regeneration in a greenhouse at the Akdeniz University, Antalya, Turkey. Selected mutants regenerated from the irradiated stolons were clonally propagated and transplanted into plastic pots for further observations of turfgrass characteristics. Survival rates of stolons exposed to 70, 90 and 110 Gy were 76%, 43% and 17% respectively, 6 weeks after treatment. Dosages of 85 and 57 Gy were determined as LD50 and LD20 for the cuttings, respectively. The linear reduction of survival rate with increasing gamma-rays was highly correlated (r2=0.99). A total of four mutant lines (0.3 % of the irradiated plants) showed a distinct dwarfed growth habit. Three of these lines were originated from 70 Gy and one from 110 Gy. These mutant lines exhibited more dwarf growth habit, higher shoot density, finer leaf texture than parental genotype. Mutant lines developed in this study can be used for the development of improved bermudagrass cultivars for landscaping and sports turf.

Phenology, biomass and productivity of sub-Antarctic Ruppia filifolia

Seagrasses play important ecological roles in shallow coastal ecosystems from tropical to sub-polar seas. Ruppia filifolia (Phil.) Skottsberg is the seagrass with the world’s southernmost distribution but with virtually unknown biology and ecology. The goal of this study was to identify the ecological roles that R. filifolia might play in sub-Antarctic environments through the assessment of the development and primary productivity of this aquatic flowering plant. We monitored biomass and shoot density, rhizome growth and the presence of reproductive structures during 1 year in Skyring Sound, sub-Antarctic Chile. Ruppia filifolia forms perennial meadows with high biomass (124–293 g DW m−2) and shoot density (1800–5300 shoot m−2), a continuous presence of vertical stems and a rhizome plus root to shoot biomass ratio >1. Plant development shows a unimodal seasonal pattern with flowering in spring, and fruiting and maximum growth during summer. An average rhizome plastochrone of 37 days and median rhizome elongation of 27.5 cm plant−1 year−1 rank R. filifolia as a slow-growing seagrass. Primary productivity varied from 0.5 to 4.2 g DW m−2 day−1, resulting in an annual primary production of 700 g DW m−2. Ruppia filifolia in sub-Antarctic environments might play ecosystem roles (carbon sequestration, sediment stabilization, structural habitat, nutrition sources) as important as those played by seagrasses in tropical or temperate coastal environments.

Registration of DALBG 1201 Hybrid Bluegrass

DALBG 1201 (Reg. No. CV-101, PI 671854) is a turf-type interspecific F1 hybrid derived from a cross between Texas bluegrass (Poa arachnifera Torr.) 20-11 (3-88) (PI 655088) as the female parent and a Kentucky bluegrass (P. pratensis L.) ecotype, CS#4, as the pollen parent. DALBG 1201 was evaluated under the designation 01-59-5 and TAES 5653. A total of 47 experimental hybrid bluegrass lines and three commercial checks, ‘Rebel Exeda’ tall fescue (Festuca arundinacea Schreb.) and ‘Reveille’ and ‘Thermal Blue Blaze’ hybrid bluegrass (P. arachnifera × P. pratensis) were evaluated at five locations (Auburn, AL, Starkville, MS, Raleigh, NC, Knoxville, TN, and Dallas, TX) from 2009 to 2012. DALBG 1201 was characterized by its superior turfgrass quality, darker green color, and higher shoot density than Reveille and Thermal Blue Blaze. Its leaf texture was finer than Rebel Exeda and similar to the hybrid bluegrass checks. Linear regression analysis for turfgrass quality indicated that DALBG 1201 was more stress tolerant compared with the three commercial checks and was highly stable across varying environmental conditions. Its superior performance over a wide range of southern test locations suggests that DALBG 1201 cool-season turf-type hybrid bluegrass is well-suited for use on lawns, landscapes, and other recreational sites across the southern United States.

Comparison of the influence of patch-scale and meadow-scale characteristics on flow within seagrass meadows: a flume study

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 516:49-59 (2014) - DOI: https://doi.org/10.3354/meps10873 Comparison of the influence of patch-scale and meadow-scale characteristics on flow within seagrass meadows: a flume study A. Adhitya1,5,*, T. J. Bouma1, A. M. Folkard2, M. M. van Katwijk3, D. Callaghan4, H. H. de Iongh5, P. M. J. Herman1 1Royal Netherlands Institute for Sea Research (NIOZ), PO Box 140, 4400 AC Yerseke, the Netherlands 2Lancaster Environment Centre, University of Lancaster, Lancaster LA1 4YQ, UK 3Department of Environmental Science, Institute for Wetland and Water Research, Faculty of Science, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands 4School of Civil Engineering, University of Queensland, Brisbane, Queensland 4072, Australia 5Institute of Environmental Sciences, CML/Conservation Biology, Van Steenis gebouw, Einsteinweg 2, PO Box 22333 CC Leiden, The Netherlands *Corresponding author: achmad.adhitya@nioz.nl ABSTRACT: Hydrodynamic processes are an important agent of stress and facilitation in seagrass meadows, but little is known about the effects of the common phenomenon of heterogeneity of seagrass meadows on their interactions with hydrodynamic processes. To address this gap in knowledge, 4 heterogeneous configurations of Posidionia oceanica mimics were analyzed in a laboratory flume. The 4 configurations were created by placing 4 boards of mimics, i.e. 2 with high shoot density (~1100 shoots m-2) and 2 with low shoot density (~400 m-2), in different patterns (checkerboard, parallel, dense-sparse, and sparse-dense). Our results show that volumetric flow rate through each canopy, which is an indicator of the rate of supply of resources transported by the flow, tended to be greater in the low-density patches, regardless of the configuration. We also found that the Reynolds stress component τRe was positive in the lower-density patches (indicating that horizontal momentum was being transferred into the patch) and negative in the high-density patches (indicating that horizontal momentum was being transferred upwards out of the patch). Our results suggest that in resource-limited environments, hydrodynamic processes favor the growth of lower-density patches in heterogeneous seagrass meadows, thereby causing meadows to become more homogeneous over time. KEY WORDS: Seagrass · Posidionia oceanica · Hydrodynamics · Heterogeneity · Patches · Shoot density Full text in pdf format PreviousNextCite this article as: Adhitya A, Bouma TJ, Folkard AM, van Katwijk MM, Callaghan D, de Iongh HH, Herman PMJ (2014) Comparison of the influence of patch-scale and meadow-scale characteristics on flow within seagrass meadows: a flume study. Mar Ecol Prog Ser 516:49-59. https://doi.org/10.3354/meps10873 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 516. Online publication date: December 03, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Unusual pattern in characteristics of the eelgrass Zostera marina L. in a shallow lagoon (Swan Lake), north China: Implications on the importance of seagrass conservation

Since the 1980s, seagrass populations have declined greatly in most coastal waters of China. Nevertheless, we documented, in this study, an unusual occurrence of the eelgrass Zostera marina L. in north China, with biomass markedly higher than other temperate areas in the world. Seasonal changes in biometric variables and the biomass of Z. marina were examined in a shallow marine lagoon of Swan Lake, an important nature reserve for swans (Cygnus cygnus). Results showed that shoot height of eelgrass varied seasonally, with maximum values (>170cm) being recorded in June 2009 and minimum values (<25cm) in January–March 2010. The highest shoot density was recorded in August 2009 (645shootsm−2) and the lowest in March 2010 (334shootsm−2). Eelgrass biomass also varied seasonally, from >1000gDWm−2 in August 2009 to <100gDWm−2 in March 2010. Carbon, nitrogen and phosphorus content in different parts of eelgrass also varied seasonally. The N and P contents in rhizomes were significantly lower than that in leaves and leaf sheaths. Annual average C/N ratios in leaves, leaf sheaths, and rhizomes were 14.99±2.97, 13.31±4.59, and 18.50±4.99, respectively; and annual average C/P ratios were 248.82±81.7, 199.8±87.5, and 289.2±95.1, respectively; the abovementioned deviations suggest P enrichment of eelgrass in the lagoon, compared with the global range for the species. Water temperature is the most important environmental factor that impacts the seasonal variation in this species. The increased distribution area and high productivity of Z. marina were mostly attributed to local conservation efforts.