Multi-locus evaluation of gastrointestinal bacterial communities from Zalophus californianus pups in the Gulf of California, México.

Background: The gastrointestinal (GI) bacterial communities of sea lions described to date have occasionally revealed large intraspecific variability, which may originate from several factors including different methodological approaches. Indeed, GI bacterial community surveys commonly rely on the use of a single hypervariable region (HR) of 16S rRNA, which may result in misleading structural interpretations and limit comparisons among studies. Here, we considered a multi-locus analysis by targeting six HRs of 16S rRNA with the aims of (i) comprehensively assessing the GI bacterial consortium in rectal samples from Zalophus californianus pups and (ii) elucidating structural variations among the tested HRs. In addition, we evaluated which HRs may be most suitable for identifying intrinsic, structurally related microbiome characteristics, such as geographic variations or functional capabilities. Methods: We employed a Short MUltiple Regions Framework (SMURF) approach using the Ion 16S™ Metagenomic Kit. This kit provides different proprietary primers designed to target six HRs of the 16S rRNA gene. To date, the only analytical pipeline available for this kit is the Ion Reporter™ Software of Thermo Fisher Scientific. Therefore, we propose an in-house pipeline to use with open-access tools, such as QIIME2 and PICRUSt 2, in downstream bioinformatic analyses. Results: As hypothesized, distinctive bacterial community profiles were observed for each analyzed HR. A higher number of bacterial taxa were detected with the V3 and V6-V7 regions. Conversely, the V8 and V9 regions were less informative, as we detected a lower number of taxa. The synergistic information of these HRs suggests that the GI microbiota of Zalophus californianus pups is predominated by five bacterial phyla: Proteobacteria (~50%), Bacteroidetes (~20%), Firmicutes (~18%), Fusobacteria (~7%), and Epsilonbacteraeota (~4%). Notably, our results differ at times from previously reported abundance profiles, which may promote re-evaluations of the GI bacterial compositions in sea lions and other pinniped species that have been reported to date. Moreover, consistent geographic differences were observed only with the V3, V4, and V6-V7 regions. In addition, these HRs also presented higher numbers of predicted molecular pathways, although no significant functional changes were apparent. Together, our results suggests that multi-locus analysis should be encouraged in GI microbial surveys, as single-locus approaches may result in misleading structural results that hamper the identification of structurally related microbiome features.

Human activities disturb haul out and nursing behavior of Pacific harbor seals at Punta Banda Estuary, Mexico.

Humans frequently interact with Pacific harbor seals (Phoca vitulina richardii) at Punta Banda Estuary, Baja California, Mexico, due to the high incidence of recreational activities people undertake there. The immediate effect of these interactions is that seals flush to the water, reducing their time on land and, probably, increasing their energy expenditure. On-land observations were used to study the impact of different sources of disturbance on seal behavior and evaluate their effect on the amount of time dedicated to nursing over three pupping seasons, (2015-2017), with 0.58-0.81 disturbance events/hour recorded over the entire sampling period. Terrestrial vehicles were the source with the highest disturbance rate (number of disturbance events/h), followed closely by pedestrians. However, the proportion of seals affected was highest when pedestrians were the disturbance source. Recovery events (seals hauling out after flushing) occurred after 34% of disturbance events, after less than half of which the same number of hauled-out seals as there were prior to the disturbance were observed. Recovery time varied among the years studied, of which 2017 saw the longest recovery time. In addition, pedestrians were the disturbance source with the longest recovery time. Given that resting on land is essential for pup survival, which depends on both the establishment of the mother-pup bond from birth and its maintenance throughout nursing, flushing behavior may have significant implications for the entire colony during the nursing season. We recorded a decrease in nursing duration, which did not return to the same level even after recovery and the resumption of nursing. Terrestrial vehicles were found to be the disturbance source that shortened nursing events most significantly.

Efecto de la reubicación de nidos en el éxito reproductivo de la tortuga marina Lepidochelys olivacea (Testudinata: Cheloniidae) / Effect of nest relocation on the reproductive success of the marine turtle Lepidochelys olivacea (Testudinata: Cheloniidae)

Resumen Introducción: Para incrementar el número de crías de tortugas marinas, es necesario mejorar estrategias de conservación, como incubación de nidos, en condiciones de vivero que contrarresten los efectos de las condiciones climáticas extremas. Objetivo: Comparar cinco parámetros de éxito reproductivo (éxito de eclosión, huevos sin desarrollo aparente, crías muertas, mortalidad embrionaria y período de incubación) de la tortuga marina Lepidochelys olivacea. Métodos: Se evaluó la incubación de nidos bajo dos períodos de reubicación de nidos (P1 ~28.8 °C agosto-septiembre y P2 ~27.1 °C octubre-noviembre, temperatura ambiental promedio, bajo condiciones de vivero, en el 2018 en Guerrero, México. Resultados: Se encontraron diferencias significativas en el éxito de eclosión y la mortalidad embrionaria entre los períodos de reubicación de nidos (P < 0.001). En P1, se observaron valores más bajos de éxito de eclosión (77.0 % P1 vs 88.6 % P2) y valores más altos de mortalidad embrionaria (13.7 % P1 vs 3.3 % P2) comparados con los de P2. Es importante señalar que, en el presente estudio la mortalidad embrionaria se presentó en una etapa tardía de desarrollo, es decir, en embriones casi completamente desarrollados. No se encontraron diferencias entre periodos respecto a los parámetros de huevos sin desarrollo aparente, crías muertas y período de incubación. Conclusiones: Las diferencias entre las condiciones ambientales durante el primer período de reubicación de nidos en comparación con el segundo período parecen afectar el éxito de eclosión y mortalidad embrionaria de L. olivacea. Por lo tanto, es importante tomar medidas al respecto durante esta etapa de incubación para tratar de mejorar la incubación de nidos bajo condiciones de vivero.

Abstract Introduction: In order to increase the number of sea turtle hatchlings, it is necessary to improve conservation strategies, such as nest incubation in hatchery conditions that counteract the effects of extreme climatic conditions. Objective: To compare five reproductive success parameters (hatching success, eggs with no apparent embryonic development, dead hatchlings, embryonic mortality, and incubation period) of the sea turtle Lepidochelys olivacea. Methods: The incubation of nests was evaluated under two periods of nest relocation, P1 ~28.8 °C (August and September) and P2 ~27.1 °C (October and November), average ambient temperature, under hatchery condition, in 2018 in Guerrero, Mexico. Results: Significant differences were found in hatching success and embryonic mortality between nest relocation periods (P < 0.001). In P1, lower values of hatching success (77.0 % P1 vs 88.6 % P2) and higher values of embryonic mortality (13.7 % P1 vs 3.3 % P2) were observed compared to those of P2. It's important pointing that, in the present study, embryonic mortality occurred at a late stage of development, that is, in almost fully developed embryos. No differences were found between periods regarding the parameters eggs with no apparent embryonic development, dead hatchlings and incubation period. Conclusions: The differences between the environmental conditions during the first period of nest relocation compared to the second period, respectively, seem to affect the hatching success and embryonic mortality of L. olivacea. Therefore, it is important to take action on this issue during this incubation stage to try to improve the incubation of nests under hatchery conditions.

Quantifying local ecological knowledge to model historical abundance of long-lived, heavily-exploited fauna.

Deriving robust historical population trends for long-lived species subject to human exploitation is challenging in scenarios where long-term scientific data are scarce or unavailable, as often occurs for species affected by small-scale fisheries and subsistence hunting. The importance of Local Ecological Knowledge (LEK) in data-poor scenarios is increasingly recognized in conservation, both in terms of uncovering historical trends and for engaging community stewardship of historic information. Building on previous work in marine historical ecology and local ecological knowledge, we propose a mixed socio-ecological framework to reliably document and quantify LEK to reconstruct historical population trends. Our method can be adapted by interdisciplinary teams to study various long-lived taxa with a history of human use. We demonstrate the validity of our approach by reconstructing long-term abundance data for the heavily-exploited East Pacific green turtle (Chelonia mydas) in Baja California, Mexico, which was driven to near extinction by a largely unregulated fishery from the early 1950s to the 1980s. No scientific baseline abundance data were available for this time-frame because recent biological surveys started in 1995 after all green turtle fisheries in the area were closed. To fill this data gap, we documented LEK among local fishers using ethnographic methods and obtained verified, qualitative data to understand the socio-environmental complexity of the green turtle fishery. We then established an iterative framework to synthesize and quantify LEK using generalized linear models (GLMs) and nonlinear regression (NLR) to generate a standardized, LEK-derived catch-per-unit-effort (CPUE) time-series. CPUE is an index of abundance that is compatible with contemporary scientific survey data. We confirmed the accuracy of LEK-derived CPUE estimates via comparisons with fisheries statistics available for 1962-1982. We then modeled LEK-derived abundance trends prior to 1995 using NLR. Our model established baseline abundance and described historical declines, revealing that the most critical (exponential) decline occurred between 1960 and 1980. This robust integration of LEK data with ecological science is of critical value for conservation and management, as it contributes to a holistic view of a species' historic and contemporary conservation status.

Estimación del descarte por exceso de captura en la pesquería industrial de cerco del stock Norte-Centro de la anchoveta peruana Engraulis ringens a partir de un programa de observación a bordo / Estimating discard excess catch in the industrial purse seine fisheries of the North-Center stock of the Peruvian anchoveta (Engraulis ringens) from an on-board observer program

En este trabajo se presenta la estimación del descarte por exceso de captura en la pesquería industrial de cerco del stock Norte-Centro de anchoveta peruana. Se define el descarte por exceso de captura, como la porción de captura que se arroja al mar cuando se ha capturado más de lo que la capacidad de bodega de la embarcación puede almacenar. El análisis de estimación para el periodo 2005 - 2014, se realizó a partir del "Programa de observadores a bordo de la flota de cerco" que ejecuta el Instituto del Mar del Perú (IMARPE), en donde 5 837 viajes, que representan el 1.6% de los viajes totales, fueron muestreados. Las metodologías utilizadas en la estimación fueron: Modelo Lineal Generalizado (GLM) y el Modelo Delta. Las estimaciones por el Modelo Delta y el GLM fueron diferentes en magnitudes pero similares en tendencias, sin embargo la evaluación del funcionamiento del Modelo Delta, indica que este modelo se ajusta mejor a los datos. El Modelo Delta estimó que la pesquería descarta por exceso de captura entre 2 954 y 199 164 toneladas, con un promedio de 121 312 toneladas para el periodo de estudio, el cual representó una tasa del 2.6% en relación a los desembarques. Se sugiere la incorporación de variables espaciales (p. ej. distancia a la costa, latitud, longitud), físicas (TSM) y del comportamiento del cardumen (p.e. agregación), para mejorar el análisis y comprender mejor el comportamiento de este tipo de descarte.

This paper presents estimates of the discard excess catch in the industrial purse seine fisheries of the North-Center stock of the Peruvian anchoveta (Engraulis ringens). Discard excess catch is defined as the portion of the catch that is thrown into the sea when has captured more than the hold capacity can store. The analysis is based on the "On-board observer of the purse seine vessels program" led by the Instituto del Mar del Peru (IMARPE), and in the period 2005 - 2014, 5837 trips were sampled, corresponding to 1.6% of the total trips. The methodologies used in the discard excess catch estimation were: Generalized Linear Model (GLM) and Delta Model. The estimations showed difference in magnitudes but similar trends, although the delta model appears to be a better alternative procedure for estimating the discard excess catch. The Delta Model estimated the purse seine fisheries discarded a range from 2954 to 199 164 tons, an average estimated 121 312 tons, which represent 2.6% of the landings in the period 2005 - 2014. Spatial variables (e.g. distance from the shore, latitude, longitude), physical (SST), and school behavior (e.g. fish aggregation) should be included to improve the analysis and a better understanding of the discard excess catch behavior.

Using allometric procedures to substantiate the plastochrone method for eelgrass leaf growth assessments.

Estimation of leaf productivity in eelgrass (Zostera marina L.) is crucial for evaluating the ecological role of this important seagrass species. Although leaf marking techniques are widely used to obtain estimates of leaf productivity, the accuracy of these assessments, has been questioned mainly because these fail to account for leaf growth below the reference mark and also because they apparently disregard the contribution of mature leaf tissues to the growth rate of leaves. On the other hand, the plastochrone method is a simpler technique that has been considered to effectively capture growth in a more realistic way, thereby providing more accurate assessments of both above- and below-ground productivities. But since the actual values of eelgrass growth rates are difficult to obtain, the worth of the plastochrone method has been largely vindicated because it produces assessments that overestimate productivity as compared to estimates obtained by leaf marking. Additionally, whenever eelgrass leaf biomass can be allometrically scaled in terms of matching leaf length in a consistent way, the associated leaf growth rates can be also projected allometrically. In this contribution, we used that approach to derive an authentication of the plastochrone method and formally demonstrate that, as has been claimed to occur for leaf marking approaches, the plastochrone method itself underestimates actual values of eelgrass leaf growth rates. We also show that this unavoidable bias is mainly due to the inadequacy of single-leaf biomass assessments in providing a proxy for the growth of all leaf tissue in a shoot over a given interval. Moreover, the derived formulae give conditions under which assessments of leaf growth rates using the plastochrone method would systematically underestimate matching values obtained by leaf marking procedures. And, assessments of leaf growth rates obtained by using the present data show that plastochrone method estimations underestimated corresponding proxies obtained allometrically (27%), or through leaf marking (35%). Allometric projection is recommended as a simpler and more effective procedure to reduce the bias in eelgrass leaf productivity estimations that associates to the use of plastochrone methods.

An evaluation of leaf biomass : length ratio as a tool for nondestructive assessment in eelgrass (Zostera marina L.).

The characterization of biomass and its dynamics provides valuable information for the assessment of natural and transplanted eelgrass populations. The need for simple, nondestructive assessments has led to the use of the leaf biomass-to-length ratio for converting leaf-length measurements, which can be easily obtained, to leaf growth rates through the plastochrone method. Using data on leaf biomass and length collected in three natural eelgrass populations and a mesocosm, we evaluated the suitability of a leaf weight-to-length ratio for nondestructive assessments. For the data sets considered, the isometric scaling that sustains the weight-to-length proxy always produced inconsistent fittings, and for leaf-lengths greater than a threshold value, the conversion of leaf length to biomass generated biased estimations. In contrast, an allometric scaling of leaf biomass and length was highly consistent in all the cases considered. And these nondestructive assessments generated reliable levels of reproducibility in leaf biomass for all the ranges of variability in leaf lengths. We argue that the use of allometric scaling for the representation of leaf biomass in terms of length provides a more reliable approach for estimating eelgrass biomass.

Surface aggregation patterns of LDL receptors near coated pits II. The retrograde membrane flow-diffusion and generalized plaque-form insertion mechanism.

This study presents a theoretical exploration of the effects of mechanisms that, in addition to diffusion, may influence the surface dynamics and display of unbound receptors in the low-density lipoprotein (LDL) endocytic cycle in human fibroblasts. The factors considered here are a transverse membrane flow and a generalized plaque-form insertion mode. The proposed model permits estimations of aggregation rates of unbound receptors in coated pits as well as pictorial representations of their expected steady-state display on the cell surface. Our findings show that this display is determined in a fundamental way by the ratio of the strength of the flow to the diffusion coefficient. For measured values of the diffusion coefficient and the estimated value of the flow rate strength (and independent of the receptor insertion mode), the display predicted by our model is consistent with the capping phenomenon, i.e., a gradated clustering in the direction of flow streamlines. There could be suitable characterizations of the receptor reinsertion mode that would produce a substantial reduction in the mean capture time of LDL receptors by coated pits. In any event, our results show that the existence of a transverse membrane flow precludes the display of steady-state plaque-form surface clusters.

An allometric method for the projection of eelgrass leaf biomass production rates.

We demonstrate that an allometric model for eelgrass leaf-growth rates can be derived from data on leaf architecture and growth form. Using this construct, we produced indirect assessments of growth rates of leaves that we call projections, which can be easily obtained in terms of allometric parameters and proxy values for leaf area, expressed as the product of leaf length and width. These projections of leaf-growth rates displayed a high level of correspondence with values observed in our data, as well as with other sets of reference data. A comparison with growth rates obtained by using the plastochrone index method showed that our model provides more accurate estimations while using a simpler methodology. Our results also show that whenever allometric parameters for the scaling of eelgrass leaf dry weight in terms of leaf area are available, the proposed model provides an accurate, cost-effective and non-destructive alternative to assessments based on traditional or plastochrone methods.

An economical non-destructive method for estimating eelgrass, Zostera marina (Potamogetonaceae) leaf growth rates: formal development and use in northwestern Baja California

Seagrass beds provide much of the primary production in estuaries; host many fishes and fish larvae, and abate erosion. The present study presents original analytical methods for estimating mean leaf-growth rates of eelgrass (Zostera marina). The method was calibrated by using data collected in a Z. marina meadow at Punta Banda estuary in Baja California, Mexico. The analytical assessments were based on measurements of leaf length and standard regression procedures. We present a detailed explanation of the formal procedures involved in the derivation of these analytical methods. The measured daily leaf-growth rate was 10.9 mm d-1 leaf-1. The corresponding value projected by our method was 10.2 mm d-1 leaf-1. The associated standard errors were of 0.53 and 0.56 mm d-1 leaf-1 respectively. The method was validated by projecting leaf-growth rates from an independent data set, which gave consistent results. The use of the method to obtain the mean leaf growth rate of a transplanted plot is also illustrated. Comparison of our leaf-growth data with previously reported assessments show the significant forcing of sea-surface temperature on eelgrass leaf dynamics. The formal constructs provided here are of general scope and can be applied to equivalent eelgrass data sets in a straightforward manner. Rev. Biol. Trop. 56 (3): 1003-1013. Epub 2008 September 30.

Las praderas de pastos marinos abaten la erosión y aportan gran parte de la productividad primaria de los esteros y son refugio de muchos peces y sus larvas. El presente trabajo introduce métodos analíticos para estimar las tasas medias de crecimiento foliar de Zostera marina L. y sus varianzas. La calibración del método se llevó a cabo utilizando datos de una pradera de esta fanerógama en el Estero de Punta Banda Baja California, México. Las referidas estimaciones analíticas, se basan en medias de longitud foliar y en procedimientos estandarizados de regresión. Dichas determinaciones son por ende no-destructivas. Se proporciona una explicación detallada de los aspectos formales de la derivación del método. El valor promedio observado de la tasa media diaria de crecimiento foliar fue de 10.9 mm d-1 leaf-1. El valor correspondiente proyectado mediante nuestro método fue de 10.2 mm d-1 leaf-1. Los errores estándar asociados fueron 0.53 y 0.56 mm d-1 leaf-1 respectivamente. Valores proyectados de la tasa media de crecimiento foliar diario utilizando datos de longitudes foliares publicadas por otros autores dieron también resultados consistentes. Se ilustra también el uso del método para proyectar la media de crecimiento foliar de una parcela transplantada de Zostera marina. La comparación de los resultados de este estudio con equivalentes reportados previamente nos permite concluir que las diferencias observadas pueden ser explicadas en función de la variabilidad de la temperatura superficial del mar en virtud del control de esta variable sobre la dinámica foliar de Z. marina. Las herramientas de estimación indirecta presentadas en este trabajo pueden aplicarse fácilmente a datos equivalentes de Z. marina.

Mortality rate estimation for eelgrass Zostera marina (Potamogetonaceae) using projections from Leslie matrices

The main goal of this study is to provide estimations of mean mortality rate of vegetative shoots of the seagrass Zostera marina in a meadow near Ensenada Baja California, using a technique that minimizes destructive sampling. Using cohorts and Leslie matrices, three life tables were constructed, each representing a season within the period of monthly sampling (April 1999 to April 2000). Ages for the cohorts were established in terms of Plastochrone Interval (PI). The matrices were projected through time to estimate the mean total number of individuals at time t, n(t) as well as mortality. We found no statistical differences between observed and predicted mean values for these variables (t=-0.11, p=0.92 for n(t) and t=0.69, p=0.5 for mean rate of mortality). We found high correlation coefficient values between observed and projected values for monthly number of individuals (r=0.70, p=0.007) and monthly mortality rates (r=0.81, p=0.001). If at a certain time t a sudden environmental change occurs, and as long as the perturbation does not provoke the killing of all the individuals of a given age i for 0 ≤ i ≤ x - 1, there will be a prevailing number of individuals of age or stage x at a time t+1. This nondestructive technique reduces the number of field visits and samples needed for the demographic analysis of Z. marina, and therefore decreases the disturbance caused by researches to the ecosystem. Rev. Biol. Trop. 56 (3): 1015-1022. Epub 2008 September 30.

El propósito principal de este estudio es el de proveer estimaciones de tasas promedio de mortalidad de tallos vegetativos de Zostera marina en una pradera cercana a Ensenada Baja California, utilizando una técnica que minimiza los muestreos destructivos para estos pastos marinos. Mediante la utilización de cohortes y matrices de Leslie, se construyeron tres tablas de vida, cada una representando a una estación dentro de período anual de muestreos mensuales (Abril 1999 a Abril 2000). Las edades de los cohortes fueron estimadas en términos de Intervalos de Plastocrono (IP). Las matrices de Leslie fueron proyectadas a través del tiempo para estimar el número total de individuos a un tiempo t, n(t) así como las tasas de mortalidad. No se encontraron diferencias significativas entre los valores medios observados y proyectados para estas variables (t=0.11, p=0.92 para n(t) y t=0.69, p=0.5 para la tasa media de mortalidad). Se encontraron altas correlaciones los valores observados y proyectados tanto en el número de individuos (r=0.70, p=0.007) como las tasas mensuales de mortalidad (r=0.81, p=0.001). Si a cierto tiempo t ocurre un cambio ambiental repentino, de tal manera que la perturbación no provoque la muerte de todos los individuos de una edad i para 0 ≤ i ≤ x-1, prevalecerá un número de individuos de edad o estadio x al tiempo t+1. Esta técnica no destructiva reduce el número de visitas al campo y de muestras necesarias para un análisis demográfico de Z. marina y por lo tanto decrece el disturbio causado al ecosistema.

An economical non-destructive method for estimating eelgrass, Zostera marina (Potamogetonaceae) leaf growth rates: formal development and use in northwestern Baja California.

Seagrass beds provide much of the primary production in estuaries; host many fishes and fish larvae, and abate erosion. The present study presents original analytical methods for estimating mean leaf-growth rates of eelgrass (Zostera marina). The method was calibrated by using data collected in a Z. marina meadow at Punta Banda estuary in Baja California, Mexico. The analytical assessments were based on measurements of leaf length and standard regression procedures. We present a detailed explanation of the formal procedures involved in the derivation of these analytical methods. The measured daily leaf-growth rate was 10.9 mm d(-1) leaf(-1). The corresponding value projected by our method was 10.2 mm d(-1) leaf(-). The associated standard errors were of 0.53 and 0.56 mm d(-1) leaf(-1) respectively. The method was validated by projecting leaf-growth rates from an independent data set, which gave consistent results. The use of the method to obtain the mean leaf growth rate of a transplanted plot is also illustrated. Comparison of our leaf-growth data with previously reported assessments show the significant forcing of sea-surface temperature on eelgrass leaf dynamics. The formal constructs provided here are of general scope and can be applied to equivalent eelgrass data sets in a straightforward manner.

Mortality rate estimation for eelgrass Zostera marina (Potamogetonaceae) using projections from Leslie matrices.

The main goal of this study is to provide estimations of mean mortality rate of vegetative shoots of the seagrass Zostera marina in a meadow near Ensenada Baja California, using a technique that minimizes destructive sampling. Using cohorts and Leslie matrices, three life tables were constructed, each representing a season within the period of monthly sampling (April 1999 to April 2000). Ages for the cohorts were established in terms of Plastochrone Interval (PI). The matrices were projected through time to estimate the mean total number of individuals at time t, n(t) as well as mortality. We found no statistical differences between observed and predicted mean values for these variables (t = -0.11, p = 0.92 for n(t) and t = 0.69, p = 0.5 for mean rate of mortality). We found high correlation coefficient values between observed and projected values for monthly number of individuals (r = 0.70, p = 0.007) and monthly mortality rates (r = 0.81, p = 0.001). If at a certain time t a sudden environmental change occurs, and as long as the perturbation does not provoke the killing of all the individuals of a given age i for 0 < or = i < or = x - 1, there will be a prevailing number of individuals of age or stage x at a time t+1. This nondestructive technique reduces the number of field visits and samples needed for the demographic analysis of Z. marina, and therefore decreases the disturbance caused by researches to the ecosystem.

Improved leaf area index based biomass estimations for Zostera marina L.

The application of special scanning technologies in plant population studies makes it now possible to offer reliable indirect estimations of Leaf Area Index (LAI). This has stimulated the adaptation of related biomass assessment methods and has provided a way to simplify tedious laboratory procedures whilst avoiding destructive sampling. Particularly, above-ground biomass for Zostera marina L. has been expressed depending linearly on Leaf Area Index. Nevertheless, we demonstrate that this approach produces biased estimations. It is also shown that expressing leaf dry weight by means of an allometric function of length and width can eliminate bias. Furthermore, the dominant term of the associated power series expansion becomes the aforementioned linear representation in terms of Leaf Area Index. The consistency of the estimation methods derived from the allometric model was tested using data from a Z. marina meadow. Consequently, the improved method is expected to become a valuable tool for the reduction of the uncertainty associated with the estimation of above-ground biomass through the use of Leaf Area Index.

An upgraded method to relocate marked shoots of the seagrass Zostera marina

This paper presents a new method for the recovery of marked seagrass blades. The introduction of a plastic belt surrounding the marked shoot at a sediment level provided a relocation arrangement which was unloosed by drag forces or grazing. The relocation method was tested on Zostera marina L. It proved to have the advantage of increasing dramatically the number of marked shoots recovered up to 100 while reducing the cost of the procedure to a minimum. An allometric model indicated that the introduced relocation method has no impact on the development of the plant.