Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Back-calculated age, hatch date, length-at-age, growth rate, and experienced temperature of young-of-year Atlantic silversides (Menidia menidia) collected during 3 successive collections in Mumford Cove, CT in fall 2015.

Young-of-year (YoY) Atlantic silversides were collected from Mumford Cove (41.32N, 72.02W), a small, salt-marsh dominated embayment in eastern Long Island Sound (Connecticut USA, 0.5 km², 1-3 m depth). From a biweekly beach seine survey (30×2m seine with 3mm mesh), three samples on 23 October, 20 November, and 18 December 2015 were used. On each date, samples were pooled from two independent seine casts. All silversides were euthanized, enumerated, measured for total length (TL) to the lower 5 mm and preserved frozen (-20°C). From each collection, ~100 individuals were selected for otolith microstructure analysis using a TL-stratified random sampling design. For each individual, we again measured TL (nearest 0.1 mm) and determined its sex via visual inspection of gonads, before extracting both sagittal otoliths. Sagittae were mounted on microscope slides using CrystalBond 509 thermoplastic cement. If equally suitable, the left or right sagitta was randomly chosen for analysis. Otoliths were hand-polished using 9 µm then 3 µm lapping films (3M) until daily increments along the entire reading axis were clearly visible under 400x magnification (Nikon Eclipse E400 compound microscope). Otoliths were measured and read across the sagittal plane from the nucleus to the dorsal or ventral otolith edge, because the more conventional core to post-rostrum axis proved to be too curved to be reliably interpretable. Increments were enumerated and measured using Image Pro Premier (V9.1) connected to a Luminera Infinity2-2 digital camera. For each otolith section, multiple focal planes were captured and merged into multi-layer images to aid the reader interpreting the otolith microstructure. The radius of the hatch-check (µm) was measured. The last growth increment was presumed to be incomplete and thus excluded from growth analyses. Increment number was assumed to correspond to an individuals’ age in days post hatch (dph). Hatch date was calculated by subtracting age from the date of collection, while the formation date of each increment was calculated by adding the increment number to the hatch date.

To estimate the thermal history of October YoY we used continuous temperature data recorded by a Manta Sub2 probe (Eureka© Water Probes) at our study site. Three small gaps in the record (<8 days) were linearly interpolated. Daily temperatures during a larger data gap (34 days, 18 June - 22 July) were estimated via linear regression between the Mumford Cove dataset and temperatures in nearby Niantic Bay (2015-2016) that were strongly correlated (TMumford= 1.07*TNiantic – 0.54 r²= 0.92, F = 6024.9, p < 0.001). Average daily temperatures were then linked to the corresponding day of increment formation for each individual. To quantify the thermal dependency of larval growth in October YoY, we calculated the mean experienced temperature during the first 30 dph for each individual and correlated it to its mean daily growth rate over the first 30dph (GR30) and its back-calculated TL at day 30 post hatch (TL30, a proxy for the end of the larval stage).

Data Processing:
The proportion of females (Nfem/Nfem+male) per 10 mm TL class in the otolith sample was used to derive sex-specific TL distributions of the population sample (beach seine), assuming sexes being randomly sampled within each TL class. Similarly, otolith-derived hatch distributions were scaled to population by applying a scale factor (SF) to each individual based on the relative frequencies (RF) of each 10 mm TL class in the population vs. otolith sample for each collection (SF = RFpopulation/RFotolith).

Only for YoY survivors from October, individuals were grouped into each of four bi-weekly hatch intervals that were chosen based on sample size and the known semi-lunar spawning periodicity of silversides. TL-at-age was back-calculated for each individual over the entire increment record (99-148dph) with the biological intercept method and an assumed length at hatch of 5 mm.

Problem Report:
As detailed in the corresponding publication, a central objective was to determine whether ages in older young-of-year Atlantic silversides could be reliably determined. Because this was found to be the case only for individuals sampled during October, but not during subsequent collections in November and December, back-calculated ages, hatch dates, length-at-age, or growth rates are only given for individuals collected in October.

BCO-DMO Processing:
- formatted all dates to yyyy-mm-dd;
- modified parameter names (replaced spaces w/ underscores; removed parens & units);
- filled in blanks with "nd" ("no data").

Description from NSF award abstract:
Coastal marine ecosystems provide a number of important services and resources for humans, and at the same time, coastal waters are subject to environmental stressors such as increases in ocean acidification and reductions in dissolved oxygen. The effects of these stressors on coastal marine organisms remain poorly understood because most research to date has examined the sensitivity of species to one factor, but not to more than one in combination. This project will determine how a model fish species, the Atlantic silverside, will respond to observed and predicted levels of dissolved carbon dioxide (CO2) and oxygen (O2). Shorter-term experiments will measure embryo and larval survival, growth, and metabolism, and determine whether parents experiencing stressful conditions produce more robust offspring. Longer-term experiments will study the consequences of ocean acidification over the entire life span by quantifying the effects of high-CO2 conditions on the ratio of males to females, lifetime growth, and reproductive investment. These studies will provide a more comprehensive view of how multiple stressors may impact populations of Atlantic silversides and potentially other important forage fish species. This collaborative project will support and train three graduate students at the University of Connecticut and the Stony Brook University (NY), two institutions that attract students from minority groups. It will also provide a variety of opportunities for undergraduates to participate in research and the public to learn about the study, through summer research projects, incorporation in the "Women in Science and Engineering" program, and interactive displays of environmental data from monitoring buoys. The two early-career investigators are committed to increasing ocean literacy and awareness of NSF-funded research through public talks and presentations.

This project responds to the recognized need for multi-stressor assessments of species sensitivities to anthropogenic environmental change. It will combine environmental monitoring with advanced experimental approaches to characterize early and whole life consequences of acidification and hypoxia in the Atlantic silverside (Menidia menidia), a valued model species and important forage fish along most of the US east coast. Experiments will employ a newly constructed, computer-controlled fish rearing system to allow independent and combined manipulation of seawater pCO2 and dissolved oxygen (DO) content and the application of static and fluctuating pCO2 and DO levels that were chosen to represent contemporary and potential future scenarios in productive coastal habitats. First CO2, DO, and CO2 × DO dependent reaction norms will be quantified for fitness-relevant early life history (ELH) traits including pre- and post-hatch survival, time to hatch, post-hatch growth, by rearing offspring collected from wild adults from fertilization to 20 days post hatch (dph) using a full factorial design of 3 CO2 × 3 DO levels. Second, the effects of tidal and diel CO2 × DO fluctuations of different amplitudes on silverside ELH traits will be quantified. To address knowledge gaps regarding the CO2-sensitivity in this species, laboratory manipulations of adult spawner environments and reciprocal offspring exposure experiments will elucidate the role of transgenerational plasticity as a potential short-term mechanism to cope with changing environments. To better understand the mechanisms of fish early life CO2-sensitivity, the effects of temperature × CO2 on pre- and post-hatch metabolism will be robustly quantified. The final objective is to rear silversides from fertilization to maturity under different CO2 levels and assess potential CO2-effects on sex ratio and whole life growth and fecundity.

Related references:
Gobler, C.J. and Baumann, H. (2016) Hypoxia and acidification in ocean ecosystems: Coupled dynamics and effects on marine life. Biology Letters 12:20150976. doi:10.1098/rsbl.2015.0976

Baumann, H. (2016) Combined effects of ocean acidification, warming, and hypoxia on marine organisms. Limnology and Oceanography e-Lectures 6:1-43. doi:10.1002/loe2.10002

Depasquale, E., Baumann, H., and Gobler, C.J. (2015) Variation in early life stage vulnerability among Northwest Atlantic estuarine forage fish to ocean acidification and low oxygen Marine Ecology Progress Series 523: 145–156.doi:10.3354/meps11142