Seabed drag coefficient over natural beds of horse mussels (Atrina zelandica)

Measurements of seabed drag coefficient, C100, were made under tidal currents at four sites in Mahurangi Harbour, New Zealand. At the first three sites the dominant roughness element was the pinnid bivalve, Atrina zelandica (horse mussel). At the fourth site, which was devoid of horse mussels but covered in cockle shells, patches of seaweed and crab burrows, C100 was smallest (0.0055), but still twice as large as the value typically applied to abiotic, flat, cohesionless seabeds (0.0025). The mean drag coefficient plus-or-minus standard error at the three sites with horse mussels was: 0.0082 ± 0.0010 (site 1); 0.0096 ± 0.0009 (site 2); 0.0115 ± 0.0016 (site 3). There were no clear differences amongst sites 1, 2 and 3 in terms of the attributes of individual horse mussels (e.g. shell height, width or orientation), which could have been used to explain the ranking of the drag coefficients. There were, however, differences amongst the three sites in terms of spatial distribution of individual bivalves. The site with the highest density of horse mussels, site 1, had the lowest drag coefficient and an areal concentration (λ) of horse mussels higher than typical values cited for the critical concentration (λc) for the onset of skimming flow over various idealized, three-dimensional roughness elements. At sites 2 and 3, the drag coefficient was given by: C100=[κ/1n (300/mkλ)]2 which was valid for λ \u3c λ c, where κ is von Karman\u27s constant, k is the horse mussel height (i.e., protrusion above the seabed), m ≈ 100 and λc ≈ 0.2. The stable eddies that are hypothesized to lodge between roughness elements at concentrations greater than λc may influence benthic community dynamics

Intertidal habitat mapping for ecosystem goods and services: Tairua harbour

In January 2013, Waikato Regional Council (WRC) contracted the National Institute of Water and Atmospheric Research (NIWA), to develop rapid assessment techniques for mapping of intertidal habitats associated with the provision of ecosystem goods and services. Ecosystem goods and services are defined as ‘the direct and indirect benefits that humankind receives or values from natural or semi-natural habitats’ and include the provision of food and raw materials, waste treatment, processing and storage, disturbance prevention, sediment retention, water filtration and regulation, nutrient regulation, gas and climate regulation, habitat structure and cultural services such as spiritual heritage and leisure and recreation (Townsend et al. 2010). Assessment techniques were to be trialled and implemented for the intertidal area of the Tairua estuary with the view of providing: • Descriptions of habitat types that may be linked to levels of ecosystem goods and services. • Descriptions of the techniques involved in differentiating and mapping habitats, and an analysis of the precision and accuracy/validity of the methods. This report documents the evolution of the methodology and a proof of concept using Tairua estuary as a test case to build a habitat map. The goal is to generate precursor maps that will facilitate the mapping of ecosystem goods and services in the near future

Species and functional trait turnover in response to broad-scale change and an invasive species

While beta diversity has been implicated as a key factor in controlling resilience of communities to stressors, lack of long-term data sets has limited the study of temporal dynamics of beta diversity. With a time series at two sites in excess of 40yr, we investigated turnover of both species and functional traits in a system stressed by eutrophication and overfishing and undergoing climate change and invasion. The two sites, although located near to each other, differ in water depth (20 cf. 35m), but both sites have displayed increased abundances of an invasive polychaete since 1990. We tested two hypotheses related to the effect of an invasive species; that taxa richness and turnover would decrease, and trait richness would increase post invasion and that trait turnover would increase between arrival and establishment of the invasive. Generally, we observed different dynamics at the two sites and responses not consistent with our hypotheses. We detected an increase in taxa richness at both sites and an increase in taxa turnover and number of traits at one site only. Trait turnover was higher prior to the invasion, although again only at one site. Disjunctive responses between species and trait turnover occurred, with the invader contributing in a nonrandom fashion to trait turnover. The lack of strong, consistent responses to the arrival and establishment of the invasive, and the decrease in trait turnover, suggests that effects of invasives are not only system- and species-dependent, but also depend on community dynamics of the invaded site, in particular the assembly processes, and historical context.Peer reviewe

ANALISIS PEMAHAMAN KONSEP MATEMATIKA SISWA DENGAN MODEL PEMBELAJARAN PROBLEM BASED LEARNING PADA POKOK BAHASAN SEGITIGA (Study deskriptif di Kelas VII SMP Negeri 2 Plered Kab. Cirebon)

Anggun Maya Sari. NIM 59451058. “Analisis Pemahaman Konsep Matematika Siswa dengan Model Pembelajaran Problem Based Learning pada Pokok Bahasan Segitiga”. (Studi Deskriptif di Kelas VII SMP Negeri 2 Plered). Pembelajaran yang efektif adalah pembelajaran yang menyediakan kesempatan kepada siswa untuk belajar mandiri, sehingga dalam prosesnya siswa dapat memperoleh pemahaman dan pengetahuan dengan lebih mendalam. Akan tetapi proses kegiatan pembelajaran matematika yang berlangsung disekolah, pada umumnya guru hanya sekedar penyampai informasi tanpa mempertimbangkan seberapa jauh pemahaman siswa terhadap konsep matematika dari pokok bahasan segitiga yang disampaikan. Tujuan penelitian ini adalah 1) mengetahui seberapa besar pemahaman konsep yang dimiliki peserta didik; 2) mengetahui factor pendukung dan penghambat peserta didik dalam memahami konsep yang diberikan; 3) mengetahui deskripsi aktivitas siswa dalam memahami konsep matematika melalui model pembelajaran Problem Based Learning; 4) mengetahui respon siswa setelah melaksanakan model pembelajaran Problem Based Learning; 5) mengetahui sejauhmana pemahaman konsep matematika siswa setelah mengikuti proses pembelajaran Problem Based Learning. Penerapan model pembelajaran Problem Based Learning (PBL) merupakan salah satu model pembelajaran yang dapat memberikan kondisi belajar aktif kepada siswa. Dengan diterapkannya pembelajaran matematika dengan model pembelajaran PBL, diharapkan dapat membantu siswa dalam memahami konsep matematika. Penelitian ini menggunakan pendekatan kualitatif dan kuantitatif dengan metode deskriptif. Pengumpulan data menggunakan lembar observasi, pedoman wawancara, angket dan tes. Informan dalam penelitian ini adalah kelas VII yang sudah dibentuk kelompok kelas, yaitu VII A, VII D dan VII F. dengan menggunakan proportionate stratified random sampling, maka dari masingmasing kelompok kelas didapat 18 siswa sebagai informan penelitian. Berdasarkan dari hasil wawancara tentang siswa dalam pemahaman konsep matematika, diperoleh siswa masih kurang dan masih perlu banyak bimbingan. Aktivitas siswa selama pembelajaran melalui model pembelajaran PBL diperoleh dari hasil lembar observasi dengan nilai rata-rata dari semua aspek sebesar 54,39% yang termasuk dalam kategori sedang. Berdasarkan angket respon siswa setelah dilaksanakan model pembelajaran PBL termasuk dalam kategori baik dengan nilai rata-rata 76,44%. Pemahaman konsep matematika siswa setelah mengikuti proses pembelajaran dengan model pembelajaran PBL diperoleh siswa lebih rajin dalam mencari bahan untuk menyelesaikan soal-soal yang diberikan dan menambah pemahaman siswa mengenai konsep matematika, meski masih belum 100% benar, dan hasil tes didapat nilai rata-rata 39% yang termasuk dalam kategori sangat kurang. Kata Kunci: Pemahaman konsep matematika, Problem Based Learning, Segitig

The Challenge of Implementing the Marine Ecosystem Service Concept

The concept of ecosystem services has gained traction as a means of linking societal benefits to the underlying ecology and functioning of ecosystems, and is now frequently included in decision-making and legislation. Moving the ecosystem service concept from theory into practice is now crucial. However, advancements in this area of research differ by ecosystem type, and marine systems lag significantly behind terrestrial counterparts in terms of understanding, implementation, and number of studies. In this paper we explore several reasons why ecosystem service research has been limited in marine systems and we outline the challenges that hinder progress. Marine systems suffer from a scarcity of spatial data relative to terrestrial counterparts. In terrestrial systems the spatial patterns of land-use/land-cover (LULC) are relatively straightforward to access via satellite and have been used as proxy indicators of service provisions. In contrast, remote sensing tools used to study the surface of the Earth are much less effective at capturing images of the seabed, and by extension marine habitats. Marine waters and their constituents are also frequently driven great distances by winds, tides, and currents. This creates a challenge for management as the identification and protection of areas where ecosystem services are exploited is not necessarily sufficient to ensure sustained service delivery. Further complications arise from the three-dimensional uses of marine systems, incorporating activities that use the sea surface, the water column and the benthic habitats below. Progress is being made as technological advancements are resulting in the acquisition of spatial data at faster rates and higher resolutions than previously possible. There is a growing capacity to map, model and value an increasing number of services with initiatives such as InVEST or principle-based modeling. We suggest that awareness is needed around the limited progress in marine systems as this could affect the way we value the biosphere and the relative proportion between biomes

Assessing Benthic Responses to Fishing Disturbance Over Broad Spatial Scales That Incorporate High Environmental Variation

Marine benthic habitats are modified by a number of human-related disturbances. When these disturbances occur at large scales over areas of high environmental variability, it is difficult to assess impacts using metrics such as species richness or individual species distributions because of varying species-specific responses to environmental drivers (e.g., exposure, sediment, temperature). Impact assessment can also be problematic when assessed at broad spatial scales because of regional heterogeneity of species pools. Even when effects on individual species can be detected, it is difficult to upscale from individual species to ecosystem scale effects. Here, we use a functional group approach to assess broad scale patterns in ecological processes with respect to fishing and environmental drivers. We used data from field surveys of benthic communities from two large, widely separated areas in New Zealand’s EEZ (Chatham Rise and Challenger Plateau). We assigned 828 taxonomic units (most identified to species) into functional groups related to important ecosystem processes and likely sensitivity to, and recovery from, fishing disturbance to the seafloor. These included: opportunistic early colonists; substrate stabilisers (e.g., tube mat formers); substrate destabilisers; shell hash-creating species; emergent epifauna; burrowers; and predators and scavengers. Effects of fishing disturbance on benthic functional composition were observed, even at this broad spatial scale. Responses varied between functional groups, with some being tolerant of fishing impacts and others showing rapid declines with minimal fishing effort. The use of a functional group approach facilitates assessment of impacts across regions and species, allowing for improved generalisations of impacts to inform management and decision making

Identifying "vital attributes" for assessing disturbance-recovery potential of seafloor communities

Despite a long history of disturbance–recovery research, we still lack a generalizable understanding of the attributes that drive community recovery potential in seafloor ecosystems. Marine soft‐sediment ecosystems encompass a range of heterogeneity from simple low‐diversity habitats with limited biogenic structure, to species‐rich systems with complex biogenic habitat structure. These differences in biological heterogeneity are a product of natural conditions and disturbance regimes. To search for unifying attributes, we explore whether a set of simple traits can characterize community disturbance–recovery potential using seafloor patch‐disturbance experiments conducted in two different soft‐sediment landscapes. The two landscapes represent two ends of a spectrum of landscape biotic heterogeneity in order to consider multi‐scale disturbance–recovery processes. We consider traits at different levels of biological organization, from the biological traits of individual species, to the traits of species at the landscape scale associated with their occurrence across the landscape and their ability to be dominant. We show that in a biotically heterogeneous landscape (Kawau Bay, New Zealand), seafloor community recovery is stochastic, there is high species turnover, and the landscape‐scale traits are good predictors of recovery. In contrast, in a biotically homogeneous landscape (Baltic Sea), the options for recovery are constrained, the recovery pathway is thus more deterministic and the scale of recovery traits important for determining recovery switches to the individual species biological traits within the disturbed patch. Our results imply that these simple, yet sophisticated, traits can be effectively used to characterize community recovery potential and highlight the role of landscapes in providing resilience to patch‐scale disturbances.Peer reviewe

Biotic interactions influence sediment erodibility on wave exposed sandflats

Biological activities in marine soft-sediments can modify the sedimentary environment through processes that change erosion rates. In low-energy environments, bioturbating macrofauna destabilizes sediments while microbes bind sediments and stabilize them. The degree to which these counter-acting processes influence sediment movement in a physically dynamic environment has not been well quantified. In a field experiment, we established 56 (1 m(2)) plots on an exposed intertidal sandflat. We used shade cloth and manipulated grazing pressure exerted by the deposit-feeding bivalve Macomona liliana (0-200 ind. m(-2)) to alter the microphytobenthic community. Three months post-manipulation, initiation of sediment transport (T-c) and change in sediment erosion rate with increasing bed shear stress (m(e)) were measured. Mean grain size, density of the spionid polychaete Aonides trifida, density of adult M. liliana, and bulk carbohydrate concentration could account for 54% of the variation in T-c (0.3-1.1 N m(-2) s(-1)). Mean grain size was the only significant predictor (p <= 0.01) of me explaining 22% of the variability (6-20 g N-1 s(-1)). T-c was negatively correlated with density of several abundant shallow- dwelling bioturbators (indicating sediment destabilization), but we did not observe the expected increase in T-c with microbial biomass. Furthermore, there was a positive correlation between adult M. liliana and T-c as well as evidence for several positive feedbacks between abundant shallow- dwelling macrofauna and microbial biomass. These study results demonstrate that despite frequent reworking by tidal currents and waves, bioturbating macrofauna are important to initiating sediment transport regardless of their effects on microbial biomass

Effect of nutrient enrichment and turbidity on interactions between Microphytobenthos and a key bivalve: implications for higher trophic levels

Benthic diatoms are a high-quality food resource providing essential fatty acids to benthic grazers. Different stressors may alter the proportion of diatoms and other microalgae and thus can affect the quality as well as quantity of food available to benthic consumers. Microphytobenthos (MPB) lipid biomarkers were assessed in a field experiment to elucidate changes to the biosynthesis of fatty acids (FA) under nitrogen (N) enrichment (three levels) at eight intertidal sites that spanned a turbidity gradient. Influences on the flow of carbon and energy were determined using FA biomarkers of a functionally important deposit-feeding tellinid bivalve (Macomona liliana). Site-specific effects of N enrichment were detected in MPB quantity and quality measurements. Enrichment generally increased MPB biomass (chl a) across all sites, while the proportion of diatom associated fatty acid biomarkers was more variable at some sites. Analysis of sediment FA biomarkers and environmental variables suggested that changes to the microbial community composition and quality were related to water clarity and mud content of the bed. The ability of the MPB to utilize the increased nitrogen, as indicated by the resource use efficiency index, was also important. Despite the increase in MPB biomass, lipid reserves in the tissue of M. liliana, a primary consumer of MPB, were reduced (by up to 6 orders of magnitude) in medium and high N addition plots compared to control plots. Further, the nutritional quality of the bivalves to higher trophic levels [indicated by a lower ratio of essential FAs (ω3:ω6)] was reduced in high treatment plots compared to control plots suggesting the bivalves were adversely affected by nutrient enrichment but not due to a reduction in food availability. This study suggests anthropogenic nutrient enrichment and turbidity may indirectly alter the structure and function of the benthic food web, in terms of carbon flow and ecosystem productivity. This may indirectly change the interactions between MPB and key bivalves as suspended sediment concentrations and nutrient enrichment continue to increase globally. This has implications for various ecosystem functions that are mediated by these interactions, such as nutrient cycling as well as primary and secondary production

Experimenting with ecosystem interaction networks in search of threshold potentials in real-world marine ecosystems

Thresholds profoundly affect our understanding and management of ecosystem dynamics, but we have yet to develop practical techniques to assess the risk that thresholds will be crossed. Combining ecological knowledge of critical system interdependencies with a large-scale experiment, we tested for breaks in the ecosystem interaction network to identify threshold potential in real-world ecosystem dynamics. Our experiment with the bivalves Macomona liliana and Austrovenus stutchburyi on marine sandflats in New Zealand demonstrated that reductions in incident sunlight changed the interaction network between sediment biogeochemical fluxes, productivity, and macrofauna. By demonstrating loss of positive feedbacks and changes in the architecture of the network, we provide mechanistic evidence that stressors lead to break points in dynamics, which theory predicts predispose a system to a critical transition