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J.H. Hudson

Publications and source records attributed to J.H. Hudson.

11 recordsLinked to original sources
USGS2015

Evidence for the assimilation of ancient glacier organic carbon in a proglacial stream food web

We used natural abundance δ 13 C, δ 15 N, and Δ 14 C to compare trophic linkages between potential carbon sources (leaf litter, epilithic biofilm, and particulate organic matter) and consumers (aquatic macroinvertebrates and fish) in a nonglacial stream and two reaches of the heavily glaciated Herbert River. We tested the hypothesis that proglacial stream food webs are sustained by organic carbon released from glacial ecosystems. Carbon sources and consumers in the nonglacial stream had carbon isotope values that ranged from -30‰ to -25‰ for δ 13 C and from -14‰ to 53‰ for Δ 14 C reflecting a food web sustained mainly on contemporary primary production. In contrast, biofilm in the two glacial stream sites was highly Δ 14 C-depleted (-215‰ to 175‰) relative to the nonglacial stream consistent with the assimilation of ancient glacier organic carbon. IsoSource modeling showed that in upper Herbert River, macroinvertebrates (Δ 14 C = -171‰ to 22‰) and juvenile salmonids (Δ 14 C = −102‰ to 17‰) reflected a feeding history of both biofilm (~ 56%) and leaf litter (~ 40%). We estimate that in upper Herbert River on average 36% of the carbon incorporated into consumer biomass is derived from the glacier ecosystem. Thus, 14 C-depleted glacial organic carbon was likely transferred to higher trophic levels through a feeding history of bacterial uptake of dissolved organic carbon and subsequent consumption of 14 C-depleted biofilm by invertebrates and ultimately fish. Our findings show that the metazoan food web is sustained in part by glacial organic carbon such that future changes in glacial runoff could influence the stability and trophic structure of proglacial aquatic ecosystems.

Limnology and Oceanography↗
USGS1990

Underwater research methods for study of nuclear bomb craters, Enewetak, Marshall Islands

Three craters, created by the explosion of nuclear fusion devices, were mapped, sampled, core drilled and excavated with airlifts at Enewetak Atoll in the Marshall Islands by using scuba and a research submersible. The craters studied were Mike, Oak, and Koa. Tests took place near sea level at the transition between lithified reef flat and unlithified lagoonal sediments, where water depth ranged from 1 to 4 m. Craters produced by the blasts ranged from 30 to 60 m in depth. The purpose of our study was to determine crater diameter and depth immediately after detonation. Observations of submerged roadways and testing structures and upturned crater rims similar to those characteristic of meteor impacts indicate that the initial, or transient, craters were smaller than their present size. At some later time, while the area was too radioactive for direct examination, the sides of the craters slumped owing to dewatering of under lying pulverized rock. Core drilling of crater margins with a diver-operated hydraulic coring device provided additional data. On the seaward margin of the atoll, opposite Mike, a large portion of the atoll rim approximately the size of a city block had slumped into the deep ocean, leaving a clean vertical rock section more than 400m high. An abundance of aggressive grey reef sharks displaying classic territorial behavior prevented use of scuba at the Mike slump site. The two-person submersible R.V. Delta provided protection and allowed observations down to 300 m. During the 6-week period of study, we made more than 300 scuba and 275 submersible dives. Mapping was with side scan sonar and continuous video sweeps supplemented by tape-recorded verbal descriptions made from within the submersible. A mini-ranger navigation system linked to the submersible allowed plotting of bottom features, depth and sediment type with spatial accuracy to within 2 m.

Conference Paper↗
USGS1990

Methods of measurement of exploratory well impacts, offshore Florida

Six offshore oil well tests were drilled off Key West in the late 1950s and early 1960s. Two wells were drilled on coral bottom, two on carbonate sand, and two on mixed turtle grass and gorgonian/sponge hardbottom. After locating the sites with a proton magnetometer; several underwater assessment methods were used to measure the ecological impacts of drilling. Because of differing environments and bottom types, no single method was applicable at every site.

Florida↗
USGS1989

A 107-year-old coral from Florida Bay: barometer of natural and man- induced catastrophes?

The 107-yr growth history of a massive coral Solenastrea bournoni from Florida Bay was reconstructed with X-ray imagery from a single 4 in. diameter (10 cm) core that penetrated the exact epicenter of the 95.3 cm high colony. Growth increments totalled 952.9 mm, averaging 8.9 mm/yr over the life of the coral. Growth rate trends in the Florida Bay coral were compared to those in a Montastraea annularis of similar age from a nearby patch reef on the Atlantic Ocean side of the Florida Keys. It was concluded that growth rate, at least in these specimens, is a questionable indicator of past hurricanes and freezes. There does appear to be, however, a possible cause-and-effect relationship between major man-induced environmental perturbations and a prolonged reduction in growth rate in each coral's growth record. -from Authors

Bulletin of Marine Science↗
USGS1982

Effects of offshore oil drilling on Philippine reef corals.

An offshore drilling site in an area of extensive live-coral bottom off NW Palawan Island, Philippines, was examined 15 months after well completion. Porites lutea growth rates showed that little suppression of head coral growth could be attributed to drilling. Diver observation, however, together with analysis of sampling transect photomosaics, revealed 70-90% reduction in foliose, branching, and plate-like corals in an iron-stained area that extended out from the wellheads in a 115 X 85-m ellipse.-from Authors

Bulletin of Marine Science↗
USGS1982

Spurs and grooves revisited: construction versus erosion, Looe Key Reef, Florida

Six of 12 core holes drilled at Looe Key Reef (24°37'18"N. 81°24'24"W) by a diver-operated coring device penetrated a spur and groove system. Drilling indicated that: (II the spurs and grooves formed over at least 5 m of carbonate reef sand: (2) the underlying Pleistocene surface is essentially flat and therefore could not control or initiate spacing of spurs or grooves; (3) only the thin seaward ends of spurs are rooted on underlying bedrock: and (4) the interior of the Millepora-encrusted spurs is composed primarily of Acropora palmata. a species no longer abundant on this reef. From the drilling of Looe Key Reef and from other observations along the reef tract, we propose that most shallow spurs and grooves in active coral reef areas of the Caribbean are constructional in origin and not initiated or controlled by bedrock topography. Spurs and grooves in non-coral reef areas adjacent to shorelines, however. are clearly of erosional origin and have a close spacing distinctly different from spurs and grooves known to be of constructional origin. These observations indicate that spurs and grooves in deeper (> 15 m) fore-reef areas off Florida, which have the same geometry as the shoreline features. are erosional in origin and therefore formed on a shoreline during a lower stand of sea level.

Florida↗
USGS1978

Oxygen and carbon isotopic growth record in a reef coral from the Florida Keys and a deep-sea coral from Blake Plateau

Carbon and oxygen isotope analysis through a 30-year (1944 to 1974) growth of Montastrea annularis from Hen and Chickens Reef (Florida Keys) shows a strong yearly variation in the abundances of both carbon-13 and oxygen-18 and a broad inverse relationship between the two isotopes. Normal annual dense bands are formed during the summer and are characterized by heavy carbon and light oxygen. "Stress bands" are formed during particularly severe winters and are characterized by heavy carbon and heavy oxygen. The isotopic effect of Zooxanthellae metabolism dominates the temperature effect on the oxygen-18/oxygen-16 ratio. The isotopic results on the deep-sea solitary coral Bathypsammia tintinnabulum , where Zooxanthellae are nonexistent, indicates that the abundance of the heavy isotopes carbon-13 and oxygen-18 is inversely related to the growth rate, with both carbon and oxygen approaching equilibrium values with increasing skeletal age.

Florida↗
USGS1977

Topographic control and accumulation rate of some Holocene coral reefs: south Florida and Dry Tortugas

Core drilling and examination of underwater excavation on 6 reef sites in south Florida and Dry Tortugas revealed that underlying topography is the major factor controlling reef morphology. Carbon-14 dating on coral recovered from cores enables calculation of accumulation rates. Accumulation rates were found to range from 0.38 m/1000 years in thin Holocene reefs to as much as 4.85 m/1000 years in thicker buildups. Cementation and alteration of corals were found to be more pronounced in areas of low buildup rates than in areas of rapid accumulation rates. Acropora palmata, generally considered the major reef builder in Florida, was found to be absent in most reefs drilled. At Dry Tortugas, the more than 13-meter thick Holocene reef did not contain A. palmata. The principal reef builders in this outer reef are the same as those which built the Pleistocene Key Largo formation, long considered to be fossilized patch reef complex.

Florida↗