Biology subjects

Chiu, G. S.

Publications and source records attributed to Chiu, G. S..

3 recordsLinked to original sources

bioRxiv2025

Survival across habitats and sizes explains ontogenetic habitat shifts in juvenile blue crabs

Juvenile organisms often shift habitat usage during ontogeny to balance changing needs for growth and refuge, yet fine-scale habitat shifts within narrow size classes remain understudied. We conducted a manipulative tethering experiment to quantify size-specific survival of juvenile blue crabs across three habitats - seagrass meadows (seagrass), salt marsh edge (SME), and unvegetated sand flats (sand) - in the York River, Chesapeake Bay, USA. We also accounted for spatial orientation, seasonality, and turbidity. Results were analyzed using Bayesian hierarchical logistic regression models. Survival varied with crab size, habitat, and time of year, with an interaction between size and habitat. Smaller juveniles had the highest survival in seagrass, but survival increased more rapidly with size in SME and sand habitats. By 33 mm carapace width (CW), relative survival rates in seagrass and SME were statistically indistinguishable. Meanwhile, survival in sand approached that of seagrass at approximately 45 mm CW. When considered alongside previous growth rate studies, these results suggest that seagrass offers a growth-survival advantage for crabs < 15 - 20 mm CW, while salt marsh and sand habitats become increasingly favorable for larger juveniles due to comparable survival and faster growth. Consequently, even across a relatively small size range of the juvenile phase, size-specific patterns in survival differ substantially across structured and unstructured habitats. Our findings align with observed patterns of size-specific habitat use and underscore the complementary nursery roles of seagrass and salt marshes, reinforcing their joint importance in habitat restoration and conservation strategies for juvenile blue crabs.

ecology↗

bioRxiv2023

Model-based evaluation of critical nursery habitats for juvenile blue crabs through ontogeny: abundance and survival in seagrass, salt marsh, and unstructured bottom

Nursery habitats confer higher food availability and reduced predation risk, thereby contributing disproportionately more individuals per unit area to the population compared with other habitats. Nursery status is inferred through evaluation of four metrics: density, growth, survival, and linkage between juveniles and adults. Moreover, organisms commonly use multiple habitats as nurseries throughout ontogeny to satisfy shifting resource requirements. To this end, we conducted manipulative and mensurative field experiments to evaluate two nursery metrics, abundance and survival, for juvenile blue crabs across multiple size classes and habitats, including structurally complex habitats -- seagrass meadows and salt marshes -- and unstructured habitat (sand flats) in the York River, Chesapeake Bay. We also considered effects of site-specific spatial orientation within the York River, seasonality, physicochemical variables, and postlarval influx. Our results showed that abundance was higher in both seagrass meadows and salt marshes relative to unstructured sand, and positively associated with turbidity and post-larval abundance. Notably, seagrass habitats harbored the highest abundances of small ([≤] 15 mm carapace width) juveniles, whereas salt marsh edge harbored the highest abundance of medium (16-30 mm carapace width) and large (31- 60 mm carapace width) juveniles. Moreover, survival was positively associated with juvenile size and structurally complex habitats relative to unvegetated controls. Seasonally, survival peaked in April, reached a seasonal minimum in August, and increased throughout fall. Finally, habitat-specific survival was dependent on spatial position: survival was elevated at upriver salt marsh and unstructured sand habitats compared to downriver counterparts. In nursery habitats of marine species, evaluation of survival, growth, abundance and ontogenetic habitat shifts has typically focused on relatively broad size ranges through the juvenile phase. Yet, ontogenetic shifts in habitat use may occur within much narrower size ranges, which has not been well studied and which is critical to the conservation and restoration of nursery habitats. We found that habitat-specific utilization rates differed by juvenile size class over a surprisingly narrow range of size, and were related to (1) the structural and biological characteristics of the nominal nursery habitats, (2) spatial gradients of environmental variables within the tributary, and (3) the likely trade-offs between growth and survival through ontogeny. Taken together, abundance and survival results indicate that seagrass meadows are key nurseries primarily for early-stage juveniles, whereas salt marshes are an intermediate nursery habitat for larger individuals to maximize growth-to-mortality ratios. Our results underscore the need to consider both habitats as critical nurseries for juvenile blue crabs throughout ontogeny.

ecology↗

bioRxiv2016

Rooting density differentiates wheat genotypes through Bayesian modeling

Wheat pre-breeders use soil coring and core-break counts to phenotype root architecture traits, with data collected on rooting density for hundreds of genotypes in small increments of depth. The measured densities are both large datasets and highly variable even within the same genotype, hence, any rigorous, comprehensive statistical analysis of such complex field data would be technically challenging. Traditionally, most attributes of the field data are therefore discarded in favor of simple numerical summary descriptors which retain much of the high variability exhibited by the raw data. This poses practical challenges: although plant scientists have established that root traits do drive resource capture in crops, traits that are more randomly (rather than genetically) determined are difficult to breed for. In this paper we develop a Bayesian hierarchical nonlinear modeling approach that utilizes the complete field data for wheat genotypes to fit an idealized relative intensity function for the root distribution over depth. Our approach was used to determine heritability: how much of the variation between field samples was purely random versus being mechanistically driven by the plant genetics? Based on the genotypic intensity functions, the overall heritability estimate was 0.62 (95% Bayesian confidence interval was 0.52 to 0.71). Despite root count profiles that were statistically very noisy, our Bayesian analysis led to denoised profiles which exhibited rigorously discernible phenotypic traits. The profile-specific traits could be representative of a genotype and thus can be used as a quantitative tool to associate phenotypic traits with specific genotypes.

plant biology↗