Hudson R. DeYoe

THE INABILITY OF THE TEXAS “BROWN TIDE” ALGA TO USE NITRATE AND THE ROLE OF NITROGEN IN THE INITIATION OF A PERSISTENT BLOOM OF THIS ORGANISM1

A planktonic alga similar in general morphology and pigments to Aureococcus anophagefferens Hargraves and Sieburth has caused persistent and ecologically damaging blooms along the south Texas coast. Experiments using 100 μM NO3−, NO2−, and NH4+ demonstrated that the alga could not use NO3− for growth but could use NO2− and NH4+. Doubling iron or trace metal concentrations did not permit growth on NO3−. Chemical composition data for cultures grown in excess NO3− or NH4+, respectively, were as follows: N·cell−1 (0.88 vs. 1.3 pg), C:N ratio (25:1 vs. 6.4:1), C:chlorophyll a (chl a) (560:1 vs. 44:1), and chl a·cell−1 (0.033 vs. 0.16 pg). These data imply that cells supplied with NO3− were N‐starved. Culture addition of 10 mM final concentration chlorate (a nitrate analog) did not affect the Texas isolate while NO3− utilizing A. anophagefferens was lysed, suggesting that the NO3− reductase of the Texas isolate is nonfunctional. Rates of primary productivity determined during a dense bloom indicated that light‐saturated growth rates were ca. 0.45 d−1, which is similar to maximum rates determined in laboratory experiments (0.58 d−1± 0.16). However, chemical composition data were consistent with the growth rate of these cells being limited by N availability (C:N 28, C:chl a 176, chl a·cell−1 0.019). Calculations based on a mass balance for nitrogen suggest that the bloom was triggered by an input of ca. 69 μM NH4+ that resulted from an extensive die‐off of benthos and fish.

DESCRIPTION AND CHARACTERIZATION OF THE ALGAL SPECIES AUREOUMBRA LAGUNENSIS GEN. ET SP. NOV. AND REFERRAL OF AUREOUMBRA AND AUREOCOCCUS TO THE PELAGOPHYCEAE1

The Texas brown tide alga (strain TBA‐2) is described as Aureoumbra lagunensis Stockwell, DeYoe, Hargraves, et Johnson, gen. et sp. nov. Pigment composition, chloroplast structure, and 18s ribosomal RNA gene sequence data indicate that A. lagunensis and the east coast brown tide alga Aureococcus anophagefferens (originally placed in the Chrysophyceae) belong in the class Pelagophyceae. The new genus Aureoumbra with A. lagunensis as the type species differs from Aureococcus in 18s ribosomal RNA gene sequence, pyrenoid form, nitrogen physiology, and possession of basal bodies. The genus Aureococcus is placed in the order Pelagomonadates and family Pelagomonadaceae while ordinal placement of Aureoumbra is deferred.

The role of freshwater inflow in lagoons, rivers, and bays

The aim of this study was to compare the impact of different freshwater inflow volumes on benthic communities and water column dynamics in different estuary classes. Benthic and water column spatial dynamics were contrasted in lagoons (with no direct inflow sources), tidal rivers that empty directly into the Gulf of Mexico, and bar-built bay systems (with direct inflow sources) along the Texas (USA) coast to determine the role of inflow in regulating ecosystem structure and function. Chlorophyll-a and nutrient concentrations were inversely correlated with salinity and were thus highest in the river systems, but lowest in lagoons. All Texas estuary types studied have conservative mixing for silicate and ammonium but are sinks for nitrite plus nitrate and phosphate. Macrobenthic production (abundance and biomass) was lowest in rivers and highest in lagoons. Diversity was low in estuaries with salinities between 1 and 17, but increased with salinities of up to 30, before decreasing in hypersaline conditions. Macrofaunal community structure divided the estuaries into two groups. The first group represented polyhaline communities and contained lagoons (East Matagorda, Matagorda, Christmas, and South Bays). The second group represented oligo-mesohaline community characteristics and contained the secondary bays (Lavaca Bay and Cedar Lakes) and rivers (San Bernard River, Brazos River, and the Rio Grande). The implications of these results for managing freshwater flows is that altered hydrology can change the character of estuarine systems regardless of their classification as bays, lagoons, or tidal rivers.

PHYLOGENY OF AUREOCOCCUS ANOPHAGEFFERENS AND A MORPHOLOGICALLY SIMILAR BLOOM‐FORMING ALGA FROM TEXAS AS DETERMINED BY 18S RIBOSOMAL RNA SEQUENCE ANALYSIS1

The 18S ribosomal RNA genes from isolates of the east coast “brown tide” alga Aureococcus anophagefferens (strain Pt‐1) and the Texas “brown tide” alga (strain TBA‐2) were sequenced and compared to the gene sequences of Pelagomonas calceolata, a member of the Pelagophyceae, and 10 other organisms. The genes of A. anophagefferens and strain TBA‐2 consisted of 1814 and 2236 bases, respectively. The difference in length was largely due to a 423‐base insert occurring in the gene of strain TBA‐2. Excluding the insert, 93% of the bases of the aligned sequences were identical. Phylogenetic analyses were performed based on two different alignment refinement methods (eye refinement and Gatesy refinement). Trees inferred from the Jukes‐Cantor distance matrices using the neighbor‐joining method were similar for both alignment methods. In both trees, A. anophagefferens, strain TBA‐2, and P. calceolata formed a monophyletic group with A. anophagefferens and P. calceolata being sister taxa and strain TBA‐2 occurring on a deeper‐rooted branch. Bootstrap data sets for both alignment methods gave strong support for the Pelagophyceae group and the branches within that group. Parsimony analyses using the two alignments gave one tree for the eye‐refined alignment and two trees for the Gatesy method. All three trees had nearly the same topology as the trees inferred from the distance method. In addition, the Pelagophyceae group and the branches within that group were supported by bootstrap analyses and decay indices. Based on the available data, A. anophagefferens and strain TBA‐2 should be placed in the Pelagophyceae but not in the same order and family as P. calceolata.

The Biological Flora of Coastal Dunes and Wetlands: Avicennia germinans (L.) L.

ABSTRACT Lonard, R.I.; Judd, F.W.; Summy, K.R.; DeYoe, H., and Stalter, R., 2017. The biological flora of coastal dunes and wetlands: Avicennia germinans (L.) L. Avicennia germinans (L.) L. is a pantropical, subtropical, and occasionally warm-temperate mangrove species that occurs on shorelines that have a broad horizontal tidal range. Also known as black mangrove, stands typically develop under anoxic, water-logged conditions in substrates of silt or clay. Black mangrove can tolerate salinity values ranging from 0 to 90 parts per thousand. Salt is excreted from salt glands on both leaf epidermal surfaces, and aerosol salt spray and salt crystals are frequently observed on the upper leaf epidermis. Avicennia germinans is viviparous. The embryos have no dormancy requirements, and there is no seed bank. This mangrove species has the northernmost distributional range of any mangrove species in North America. It occurs in Louisiana and northern Florida. Color-infrared photography and airborne video imagery techniques have been used successfully to map stands of black mangrove on subtropical coastal shorelines. Reforestation efforts using seedlings and saplings have been successful in several areas of the tropics and subtropics. Avicennia germinans stands play an important role in ecosystem functions as a natural barrier to coastal erosion caused by tropical storms, as habitat for a wide range of organisms in intertidal food chains, and as a carbon repository.

Flowering and seed production in the subtropical seagrass, Halodule wrightii (shoal grass)

Abstract Reproductive structures of the seagrass, Halodule wrightii Ascherson (shoal grass) are cryptic and ephemeral, but were found on several occasions at several sites over more than a decade in the subtropical Laguna Madre (USA). Structures align with descriptions for H. wrightii. Male, but no female flowers were found, but the numerous fruit-bearing shoots imply the occurrence of pistillate flowers. Mean seed bank density was 890 seeds m-2 (1900–5200 m-2). Sexual reproduction in H. wrightii is more common than previously believed and the seed bank reserve may contribute to its ecological role as a colonizer of disturbed sediments.

Range extension of the macroalgae Anadyomene stellata (Wulf. In Jacquin) C. Agardh and re-appearance of Caulerpa sertularioides (S. G. Gmel.) M. Howe in the Lower Laguna Madre, Texas

Abstract We report one new species of macroalgae, Anadyomene stellata, for the Lower Laguna Madre of Texas, and range extensions that have occurred in the past 16 years for this and four other green algae. Anadyomene stellata occurs only as an epiphyte on the red macroalgae, Digenia simplex. Caulerpa sertularioides has not been seen in the Lower Laguna Madre since 1962. It has either been present in cryptic habitats for 50 years near the Lower Laguna Madre or has recently expanded its range again into the Lower Laguna Madre. Ecological consideration of the presence of these species is discussed.