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Morphology and physiology are two key aspects of the adaptation of kelp to varying environments. Some of these kelp responses to co-occurring highly hydrodynamic condition and high nutrient availability are well documented, but little is known about how these factors affect frond surface shape, particularly in the central frond. In this study, morphological and physiological traits of acclimatized Saccharina latissima (Phaeophyceae) (three size classes: 44.14 ± 1.15 cm, 29.60 ± 0.75 cm, and 16.07 ± 0.45 cm) were compared after 56 days under fully controlled conditions of waves or no waves, and high or low nutrient availability (i.e., LN-NW, LN-W, HN-NW, and HN-W treatments). Waves primarily increased frond biomass, elongation rate, and carbon to nitrogen ratio (C:N ratio) and induced both a greater variety in and rougher frond surface shapes. The fastest, second-fastest, and slowest growth rates were observed in the HN-W, LN-W, and LN-NW treatments, respectively. The highest C:N ratio was observed in the LN-W treatment. Together, these results seem to suggest that the thready and spring-like shapes found in the central frond (i.e., rougher frond surface) in wave-exposed conditions can at least partly compensate for low nutrient availability by enhancing nutrient and photon acquisition, particularly in low nutrient conditions. Additionally, large individuals showed significantly larger and heavier fronds compared with other size classes, and the meristematic sections of fronds had the most variance in frond surface shapes and highest C:N ratios compared with distal and mid-sections. Together, these results indicate that frond surface shapes in the newly formed central frond of S. latissima can be regarded both as possessing high morphological and physiological plasticity that enables kelp to cope with contrasting environments. [ABSTRACT FROM AUTHOR]

Blood biochemical profile can be used to evaluate the health status of fish and ambient environmental conditions. However, it is not well known in the aquaponic systems, let alone their differences between hydroponic and aquatic plants. A 5-month trial was conducted to investigate the changes in the growth performance and blood index of Qihe crucian carp Carassius auratus in eight aquaponic systems (control, Ipomoea aquatica, Lactuca sativa, Lemna minor, Amaranthus tricolor, Ceratophyllum demersum, Vallisneria spiralis, and C. demersum-net, indicated by CK, Ia, Ls, Lm, At, Cd, Vn, and Cd-ns). Results showed that weight gain rate and specific growth rate did not significantly differ among the eight groups. However, most blood parameters significantly differed among the eight groups. The glucose level and activities of alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase were generally larger in Cd, Lm, Vn, and CK groups, and smaller in Ia, Ls, or At groups. Additionally, the triglyceride, cholesterol, albumin, and albumin/globulin were mostly elevated in Ia and At groups. Moreover, the creatinine, total proteins, and globulin levels peaked in Vn group. These findings showed that the blood biochemical profile was more sensitive than the growth performances and that hydroponic plants can induce a higher production and more healthy status of Qihe crucian carp C. auratus when compared with aquatic plants or no plants. [ABSTRACT FROM AUTHOR]

Few studies have focused on the biomechanical responses of submerged, rosette-forming macrophytes to wave action, water depth, or their co-occurrence in naturally eutrophic systems. The plant architecture, root anchorage strength-related traits, leaf morphology, and biomechanics of Vallisneria natans inhabiting a range of water depths were examined along three transects (T1, T2, and T3) in a eutrophic lake, Lake Erhai, in Yunnan Province, China. These transects were exposed to weak wave action and hyper-eutrophication (T1), moderate wave action and eutrophication (T2), or strong wave action and eutrophication (T3). The results showed that V. natans was mainly distributed at intermediate depths, with the widest colonization depth in T1. The values of plant architecture, root anchorage strength-related traits, leaf morphology, and biomechanics were generally highest in T3 and smallest in T2. Along the depth gradient, these values were generally highest at 3.5, 2.5, and 2.5 m for the plants growing in T1, T2, and T3, respectively. These findings suggest that V. natans adopts a “tolerance” strategy to cope with the effects of strong wave action in eutrophic habitats and an “avoidance” strategy when exposed to moderate wave action in eutrophic areas. Since the absence of an avoidance strategy increases the resistance to low-light stress at the expense of increased drag forces, there is a limit to the wave action that V. natans can withstand. This study indicates that biomechanics could be important when determining the distribution pattern of V. natans in Lake Erhai. [ABSTRACT FROM AUTHOR]

The reaction-transport model is widely used to identify and quantify dissolved chemical species in sediment porewaters. In this paper, a modularized code framework of diagenetic model was proposed as a diagnostic tool to fit the porewater profiles in marine sediments. Based on the conservation principle of the finite volume method, we combined the discretized diagenetic equations with various geochemical reactions, including but not limited to methanogenesis, sulfate reduction, etc.. The code was organized in object-oriented FORTRAN and verified with literature parameters, which proved its robustness and effectiveness. Finally, three different sites (IODP Expedition 311 Site U1327, UBGH2-1_1, ODP Leg204 Site 1245) are exemplified as case studies. [ABSTRACT FROM AUTHOR]

As an endemic species of freshwater gastropods in China, Bellamya quadrata plays an important role in ecosystem service provision and commercial importance. However, the species is overharvested and its natural habitats are under severe threat due to fragmentation and loss. To estimate the genetic diversity and population structure of B. quadrata, 285 individuals from eight lake populations across middle and lower Yangtze River were sampled. Seven microsatellite loci were genotyped. Our results showed that (i) the genetic diversity of B. quadrata was high in most of the studied populations, yet effective population sizes appear to be rather small in some populations; (ii) low levels of genetic differentiation exists among populations but gene flow was generally high; (iii) no clear geographic or genetic structure was observed in the studied region, implying mechanisms (zoochoric dispersal and anthropogenic translocations) that enhance dispersal and gene flow have promoted population connectivity. However, the comparatively high genetic diversity of B. quadrata could be attributed to a lag phase, suggesting that the genetic diversity of this species may be lost in the future and the priorities for conservation of B. quadrata are necessary. [ABSTRACT FROM AUTHOR]

Submerged macrophytes mainly distribute in the wind-protected littoral zones, rather than continuously distribute around the lake due to mechanical damage by strong wave. However, it is unknown how the biomechanical properties, the key targets against mechanical stress, contribute to its survival and distribution in natural aquatic ecosystem. In this study, the distribution, plant growth, and leaf biomechanical and morphological traits of different segments of Vallisneria natans were examined at 25 sites with three wind strength [sites exposed to strong ES wind (HW), sites exposed to moderate ES wind (MW) and sites sheltered by lakeshore with weak wind disturbance], in Lake Erhai, of Yunnan Province, China. Results showed that V. natans mainly distributed in the wind-protected eastern and northern littoral zones within 5 m water depth. The smallest plant growth, strongest and least flexible leaves were at MW, indicating that V. natans is prone to dominate the littoral zones exposed to strong but short wave. Additionally, the high plant growth and relatively stronger and less flexible leaves at HW suggested that the maximization of photosynthesis was at the cost of reduced biomechanical properties and increased drag forces from similar waves, which were unfavourable to complete their life cycles and ultimately reduce the survival and distribution of V. natans under strong wave disturbance. The significant associations between the biomechanical and morphological traits may trigger trade-offs between the mechanical resistance and other plant functions, such as photosynthesis, ultimately determining survival and distribution of submerged macrophytes in natural aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Variability in biomass allocation and growth rate of submersed macrophytes along water depth gradients may lead to different carbon (C), nitrogen (N) and phosphorus (P) stoichiometric characteristics. We conducted a field investigation to evaluate long-term effects of water depth on C, N and P stoichiometry of three submersed macrophytes, Potamogeton maackianus, Myriophyllum spicatum and Ceratophyllum demersum. The results indicated that shoot C:N, C:P and N:P of the plants tended to increase with elevated water depths, and patterns of biomass allocation along water depth gradients were more important than biological dilution of increased growth rates in affecting shoot C:N:P stoichiometric characteristics of the plants. Partial correlation analysis using shoot height and biomass as covariates revealed that water depth significantly affected C:P ratios in shoots of P. maackianus and M. spicatum and C:N ratio in shoots of M. spicatum, but did not affect N:P ratios of all the plants. Shoot stoichiometry of M. spicatum was most sensitive in response to water depth, followed by P. maackianus, and that of C. demersum was really unchanged with elevated water depths. Our results suggested that strategies in biomass allocation in organs, which depend largely on the species identity, rather than growth rates of the plants, contributed mainly to variation in the observed element stoichiometry along the water depth gradients. [ABSTRACT FROM AUTHOR]

Decline of submersed macrophytes has occurred in eutrophic lakes worldwide. Little is known about effects of nutrient enrichment on biomechanical properties of submersed macrophytes. In a 30-day experiment, Myriophyllum spicatum was cultured in aquaria containing two types of sediment (mesotrophic clay vs. fertile loam) with contrasting water NH concentrations (0 vs. 3.0 mg L NH-N). The plant growth, shoot and root morphology, stem biomechanical properties, and stem total nonstructure carbohydrates content (TNC) were examined. The NH-enriched water, particularly combined with the fertile sediment, caused adverse effects on M. spicatum as indicated by reductions in the growth, stem biomechanical properties (tensile force, bending force and structural stiffness), and TNC content. These results indicate that increased sediment fertility and water NH-enrichment made the plant more fragile and vulnerable to hydraulic damage, particularly for the upper stem, implying that M. spicatum was prone to uprooting and fracture by hydraulic force, and the broken fragment from parent shoot of M. spicatum might have low-survival potential due to its low-TNC content. This may be a mechanical aspect for the decline of submersed macrophytes and makes it more difficult to restore submersed vegetation in the eutrophic lakes. [ABSTRACT FROM AUTHOR]

Little is known about the mechanical resistance response of submerged macrophytes to floods. An experiment was conducted to investigate the plant growth, root anchorage strength, and stem tensile properties of five submerged macrophytes under three initial water levels (1.0, 2.5, and 4.0 m) with four water level fluctuation speeds (0, 5, 15, and 25 cm d). Our results demonstrate that the biomass, relative growth rate, root anchorage strength, and stem tensile properties of the five species decreased with increasing initial water level, suggesting that deep water can inhibit plant growth and decrease their mechanical resistance. Floods weakened the stem tensile properties and strengthened the root performances of Myriophyllum spicatum, Hydrilla verticillata, and Potamogeton malaianus in shallow water. However, floods induced opposite mechanical resistance responses from plants in deep water, indicating a possible trade-off between stem breakage and uprooting under flooding conditions. M. spicatum, Ceratophyllum demersum, and P. malaianus were more tolerant of deep water and flood intensity than Potamogeton maackianus and H. verticillata, as indicated by their larger biomass, plant heights, stem tensile properties, and root anchorage strength. This is the first article that mechanically explains the competitive capability and survival potential of submerged macrophytes to water depth and flood intensity. [ABSTRACT FROM AUTHOR]