Search for: All records

Tidal marshes in the Chesapeake Bay are vulnerable to the accelerating rate of sea-level rise (SLR) and subsidence. Restored and created marshes face the same risks as natural marshes, and their resilience to SLR may depend upon appropriate design and implementation. Here, the Coastal Wetland Equilibrium Model (CWEM) was used to assess the resilience of tidal marshes at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island (PI) in mid-Chesapeake Bay, MD, where dredged material from navigation channels is being used to create new tidal marshes planted withSpartina alterniflorain the low marsh andS. patensin the high marsh. The site is microtidal with low inorganic sediment inputs, where the rate of marsh elevation change is dominated by the production of organic matter and, therefore, is proportional to net ecosystem production (NEP). The model demonstrated the importance of marsh development for surface elevation gain. In created marshes, the buildout of belowground biomass adds volume and results in faster growth of marsh elevation, but the gains slow as the marsh matures. Elevation gain is the lessor of the recalcitrant fraction of NEP sequestered in sediment or the rate of increase in accommodation space. Marshes can keep up with and fill accommodation space with sequestered NEP up to a tipping point determined by the rate of SLR. The PI low marsh platform was forecasted to drown in about 43 years after construction at the current rate of SLR. Marsh loss can be mitigated by periodic thin layer placement (TLP) of sediment. CWEM was used to simulate PI marsh responses to different TLP strategies and showed that there is an optimal design that will maximize carbon sequestration and resilience depending on the trajectory of mean sea level.

 

The theory describing the evolution of offspring size often assumes that the production cost per unit volume is the same for small and large offspring. However, this may not be true if indirect costs of reproduction (e.g., material and energetic costs of supporting offspring development) scale disproportionately with offspring size. Here we show how direct and indirect costs of reproduction can be explicitly modeled within the Smith–Fretwell framework and how observations of size-number relationships can thus be used to evaluate indirect costs. We applied this analysis to measures of egg volume and fecundity for over 300 individuals of a coastal fish species and found that the tradeoff was much stronger than the expected inverse (fecundity scaled with volume−1.843). Larger offspring were thus more expensive to produce. For our study species, an important indirect cost was that larger eggs were accompanied by disproportionately more ovarian fluid. Calorimetry and removal experiments were used to further measure both the energetic costs and fitness benefits of ovarian fluid. In addition, we show that indirect costs of reproduction can intensify size-number tradeoffs in a variety of fishes. Indirect costs of reproduction can be large and may therefore play an important role in the evolution of offspring size.

 

A network of 15 Surface Elevation Tables (SETs) at North Inlet estuary, South Carolina, has been monitored on annual or monthly time scales beginning from 1990 to 1996 and continuing through 2022. Of 73 time series in control plots, 12 had elevation gains equal to or exceeding the local rate of sea-level rise (SLR, 0.34 cm/year). Rising marsh elevation in North Inlet is dominated by organic production and, we hypothesize, is proportional to net ecosystem production. The rate of elevation gain was 0.47 cm/year in plots experimentally fertilized for 10 years with N&P compared to nearby control plots that have gained 0.1 cm/year in 26 years. The excess gains and losses of elevation in fertilized plots were accounted for by changes in belowground biomass and turnover. This is supported by bioassay experiments in marsh organs where at age 2 the belowground biomass of fertilizedS. alternifloraplants was increasing by 1,994 g m⁻² year⁻¹, which added a growth premium of 2.4 cm/year to elevation gain. This was contrasted with the net belowground growth of 746 g m⁻² year⁻¹in controls, which can add 0.89 cm/year to elevation. Root biomass density was greater in the fertilized bioassay treatments than in controls, plateauing at about 1,374 g m⁻²and 472 g m⁻², respectively. Growth of belowground biomass was dominated by rhizomes, which grew to 3,648 g m⁻²in the fertilized treatments after 3 years and 1,439 g m⁻²in the control treatments after 5 years. Depositional wetlands are limited by an exogenous supply of mineral sediment, whereas marshes like North Inlet could be classified as autonomous because they depend on in situ organic production to maintain elevation. Autonomous wetlands are more vulnerable to SLR because their elevation gains are constrained ultimately by photosynthetic efficiency.

 

Wetland management practices often alter habitat characteristics to improve the function of the wetland (e.g., removing emergent vegetation for aesthetics or dredging for fish stocking), potentially at the cost of reducing habitat quality for wetland-dependent species such as freshwater turtles. We identified wetland and surrounding landscape characteristics related to painted turtle (Chrysemys picta) and snapping turtle (Chelydra serpentina) relative abundance and snapping turtle movement among wetlands. We surveyed turtles at 29 wetland sites (0.04–1.71 ha) in a mixed-use watershed in north-central West Virginia, USA, where hardwood forests and wetlands have been heavily fragmented by agriculture and roads. We also applied radio transmitters to 33 adult snapping turtles (17 females and 16 males) across 17 wetlands. Snapping turtle relative abundance was best estimated with mean substrate depth, mean wetland depth, and minimum distance from roads. Painted turtle relative abundance was best estimated with the null model. We documented movement among wetlands for 22 snapping turtles (67%), including 10 females and 12 males. The probability of inter-wetland movement decreased with increased minimum distance from wetlands. Our results suggest that the focal turtle species readily used shallow, mucky wetlands with deep substrate and that increasing the density of wetlands could increase snapping turtle population connectivity. Managers could consider restoring a diversity of wetland types that result in reduced travel distance between wetlands and that collectively have characteristics conducive to multiple species.

 

Over the last 2 decades, routine collections in the Hawaiian Archipelago have expanded to mesophotic reefs, leading to the discovery of a new red algal genus and species, here described asAnunuuluaehu liulagen. et sp. nov. This study provides a detailed genus and species description and characterizes chloroplast and mitochondrial organellar genomes. The new genus,Anunuuluaehu, shares many characteristics with the family Phyllophoraceae and shows close similarities toArchestennogrammaandStenogramma, including habit morphology, nemathecia forming proliferations at the outer cortex with terminal chains of tetrasporangia, and carposporophytes with multi‐layered pericarps. The single species in this genus exhibits distinctive features within the Phyllophoraceae: the presence of single‐layer construction of large medullary cells and the development of long, tubular gonimoblastic filaments. Multi‐gene phylogenetic analyses confirmed it as a unique, monophyletic lineage within the family. Cis‐splicing genes, interrupted by intron‐encoded proteins within group II introns, are present in both the chloroplast and mitochondrial genomes ofA. liula. Notably, a specific region of thecoxI group II intron exhibits similarity to fungal introns.Anunuuluaehu liulais presumed to be endemic to the Hawaiian Archipelago and thus far is known to live solely at mesophotic depths from Hōlanikū to Kaho‘olawe ranging from 54 to 201 m, which is the deepest collection record of any representative in the family. Overall, this study enhances our understanding of the genomic and taxonomic complexities of red algae in mesophotic habitats, emphasizing the significance of continued research in this area to uncover further insights into evolutionary processes and biogeographic patterns.

 

The existence of a vast nova shell surrounding the prototypical dwarf nova Z Camelopardalis (Z Cam) proves that some old novae undergo metamorphosis to appear as dwarf novae thousands of years after a nova eruption. The expansion rates of ancient nova shells offer a way to constrain both the time between nova eruptions and the time for post-nova mass transfer rates to decrease significantly, simultaneously testing nova thermonuclear runaway models and hibernation theory. Previous limits on the expansion rate of part of the Z Cam shell constrain the inter-eruption time between Z Cam nova events to be >1300 yr. Deeper narrow-band imaging of the ejecta of Z Cam with the Condor Array Telescope now reveals very low surface brightness areas of the remainder of the shell. A second, even fainter shell is also detected, concentric with and nearly three times the size of the ‘inner’ shell. This is the first observational support of the prediction that concentric shells must surround the frequently erupting novae of relatively massive white dwarfs. The Condor images extend our Z Cam imaging baseline to 15 yr, yielding the inner shell’s expansion rate as v = 83 ± 37 km s−1 at 23 deg south of west, in excellent agreement with our 2012 prediction. This velocity corresponds to an approximate age of $t = 2672^{-817}_{+2102}$ yr. While consistent with the suggestion that the most recent nova eruption of Z Cam was the transient recorded by Chinese imperial astrologers in the year 77 bce, the age uncertainty is still too large to support or disprove a connection with Z Cam.

 

Changing climates can influence species range shifts and biological invasions, but the mechanisms are not fully known. Using the model speciesPhragmites australis(Cav.) Trin. ex Steud. (Poaceae), we conducted a global analysis of climate and plant native and introduced cytotypes to determine whether this relationship influences population distributions, hypothesizing that smaller genomes are more common in regions of greater environmental stress. First, we identified 598Phragmites australisfield-collected native and introduced genome size variants using flow cytometry. We then evaluated whether temperature and precipitation were associated withP. australismonoploid genome size (Cx-value) distributions using Cx-value and Worldclim data. After accounting for potential spatial autocorrelation among source populations, we found climate significantly influenced Cx-value prevalence on continents. The relationships of Cx-value to temperature and precipitation varied according to whether plants were native or introduced in North America and Europe, and Cx-values were strongly influenced by precipitation during the dry season. Smaller plant monoploid genome size was associated with more stressful abiotic conditions; under extreme high temperatures and under drought, plants had smaller Cx-values. This may influence genome dominance, biological invasions, and range expansions and contractions as climate change selects for genome sizes that maximize fitness.

 

Just 10 recurrent novae (RNe) – which erupt repeatedly on time-scales shorter than one century – are known in our Galaxy. The most extreme RN known (located in the Andromeda galaxy), M31N 2008-12a, undergoes a nova eruption every year, and is surrounded by a vast nova ‘super-remnant’, 134 pc in extent. Simulations predict that all RNe should be surrounded by similar vast shells, but previous searches have failed to detect them. KT Eri has recently been suggested to be a RN, and we have used the Condor Array Telescope to image its environs through multiple narrow-band filters. We report the existence of a large (∼50-pc diameter), H $\, \alpha$-bright shell centred on KT Eri, exactly as predicted. This strongly supports the claim that KT Eri is the 11th Galactic recurrent nova, and only the second nova known to be surrounded by a super-remnant. SALT spectra of the super-remnant demonstrate that its velocity width is consistent with that of M31-2008-12a.

 

Deforestation and climate change are expected to alter fire regimes along the Cerrado-Amazon transition, one of the world’s most active agricultural frontiers. Here we tested the hypothesis that the time since land-use transition (age of frontier) and agricultural intensification also drive changes in the region’s fire regimes by reducing fire probability in both drought and non-drought years. We modeled fire probability as a function of the time since land-use transitions based on MapBiomas Project datasets from 1986 to 2020. We find that, while burned area declined as pasturelands aged and croplands advanced, deforestation abruptly increased fire activity before (Amazon: 4 years; Cerrado: 3 years) and after (Amazon: 8 years; Cerrado: 7 years) land clearing for pasture, especially in the Amazon. Additionally, the combination of ignition risk, drought, and air-dryness increased the likelihood of large extents of burned areas associated with deforestation. Incorporating frontier age as a proxy for governance in fire modeling is crucial, given the ecological implications of changing fire regimes despite declining rates of fire probability. Most importantly, protecting against deforestation and preserving native vegetation are vital.